I've spent the last 12 days cataloguing gcl's failures in ansi-tests. Having gone through all 1900+ failures, I've found there appear to be about 284 distinct bugs (plus any bugs not detected by the tests or masked in the test suite by other failures.) The biggest improvements in failure numbers would come from implementing READTABLE-CASE and the proper return value for FORMATTER functions; the deepest issues probably involve the type system (GENERIC-FUNCTION should be a subtype of FUNCTION, for example, and FUNCTION should not intersect the type CONS.)