Raph, about the Epson Stylus Photo 2200: the light black ink isn't quite as perfect a solution as it looks at first glance. The problem with the 2200 is that the color inks alone have a cyan cast, and the light black and photo black inks have a brown cast to compensate. On Epson's other printers, Gimp-Print doesn't replace composite gray with black ink until quite a bit of CMY ink is used. On the 2200, that's not an option: you pretty much have to use light black ink for even very light gray, mixed with color ink. I've found that we can get away with cheating slightly (.01 of maximum density) without getting much of a color cast, but using composite-only ink at more than that is asking for trouble.
The light black dots are darker than the light cyan, light magenta, and yellow dots, so they're actually more visible. The upshot is that I haven't been able to achieve quite the smoothness of texture with the 2200 as I can with the 870, say.
The more interesting issues are with the choices of darker black ink. There are two choices available: photo black and matte black. The matte black ink is considerably darker, and is neutral in tone, while the photo black ink is rather brownish in color and will not produce anything close to a solid (or neutral) black without CMY inks in the same proportion (about 2 parts black for 1 part CMY is what I've found). The matte black ink doesn't actually seem to be all that dark either, at least on the papers I've tried. It's OK on Radiant White Watercolor Paper, but on Heavyweight Matte it requires extra black ink to achieve a good black.
Epson's real intent with this somewhat odd inkset appears to be twofold: to improve the blue and green gamut (where inkjets tend to be weak) and to allow toning photographic prints by adjusting the proportions of light vs. dark ink. I'm actually somewhat tempted to add a tone control (warm to cold) to Epson printers using UltraChrome inks in Gimp-Print, but that's still fairly low on my list of priorities.
What's also truly fascinating about this printer is the extreme color gamut -- it simply produces much more saturated output than any other Epson printer I've tried. This is particularly interesting because the UltraChrome inks are pigment-based, and that usually leads to a smaller gamut.
BTW, for anyone who notices that the 2200 is capable of 2880x1440 DPI while the 870 can only do 1440x720 DPI, and that it therefore sounds like the 2200 is rather lacking in comparison to a much older printer, that's a wrong interpretation. The smallest drop size the two printers use is both 4 pl, and that's more or less what limits the highlight smoothness. The difference is that the 870 needs three drop sizes, roughly 4, 8, and 12 pl, in order to deposit enough ink, while the 2200 needs only the smallest drop size. The larger dots are only used in dark areas, so they're effectively hidden. The higher resolution of the 2200 does allow more places on which to deposit a dot, which theoretically allows for better dithering placement and higher print resolution. However, with a good dither algorithm such as Raph's excellent EvenTone Screen, 1440x720 is quite sufficient. For photographs, the high print resolution doesn't matter, although for line art with extremely fine detail it could make a difference. In practice, the 2200 is almost as good at 720 DPI as it is at 2880x1440 DPI, and 4x faster (that's not a typo; the details of why are rather boring). The 870, in contrast, cannot effectively use the smallest drop sizes at 720 DPI (it uses drops of approximately 6, 12, and 24 pl), and the quality at 720 DPI is significantly degraded.
The 2200 is in fact a spectacular printer, but it has its quirks. Quirks or no, it's still a lot easier to produce a neutral grayscale on the 2200 than it is on the 870.
One thing that's somewhat unfortunate is that I have yet to figure out how to print full bleed to the top and bottom of the page. Someone sent me a print file, and it appears that there's a completely undocumented remote mode command (SN followed by something like 45 data bytes) that enables it. Changing a byte within that command disabled the full bleed. I'd like to know what that's all about.
Epson Stylus Photo 960
In contrast, I'm rather disappointed by this printer. It has a tiny 2 pl drop size, which is almost invisible under a high quality 5x loupe. It does produce very smooth highlights, but it's very hard to get a neutral grayscale from it. The workaround is to use much more dark ink, which somewhat negates the advantage of the small drops in the midtones, which therefore are actually typically grainier than the highlights.
Due to this, it really is necessary to use 2880x1440 DPI to get the highest quality; 1440x720 DPI requires using 4, 8, and 16 pl drops, which completely negates the advantage of this printer. In addition, despite the difficulty of eliminating color casts, this printer also has a markedly smaller gamut than the 2200 (which as I noted above has a really huge gamut) and the 870. This is particularly apparent in the reds. Interestingly enough, though, it does produce a very solid black.
This is a printer that could really use a light black ink.
Other Interesting Printers
Epson just announced the Stylus Pro 4000. If you're a fan of UltraChrome inks, the specs will simply blow you away. 3.5 pl, 8 separate ink tanks (lets you have both matte and photo black installed, or 2xCMYK cartridges for more throughput for proofing). Very complicated beast, but it sounds like it's quite a machine.
Epson has introduced a whole bunch of printers in Japan whose specs blow away anything available in the US. The PM-970C and PM-980C, for example, are 7-color, 1.8 (!) pl printers with gigantic print heads, which will deliver tremendous print speed in draft mode and some improvement at 2880x2880 (!) DPI. It uses a dark yellow (!) 7th ink, which apparently is used to improve skin tones. I think it would have potential to improve red, yellow, and green somewhat.
The site, by the way, is called I Love Epson. No, I can't read Japanese, and unfortunately they've Flashified the site a lot, making it harder to get around. However, they've recently introduced a line of printers spearheaded by the PX-900G, and some of the specs on these things are incredible (1.5 pl, for example).
Progress on the next release (4.4 or 5.0) is slower than I'd like. For one, we're having problems with recent 4.3 releases on Macintosh OS X; 4.3.18 works fine if you drag and drop files onto the Print Center, but printing from applications doesn't work. I suspect a PPD problem of some kind, but we haven't yet managed to debug it. I consider this to be a hard alpha stopper; OS X users are very important.
There's also project fatigue; a lot of people who have been working on it for a while are less active now. I myself am getting fatigued. Maybe it's time to move on after this release, and either take a break for a while or find something else to do. I've been working on this for more than 4 years now. That's a lot of time.