A very expensive, somewhat bugged product. The Windows version crashed every PC we tried it on. ''No wonder, Windows!" Allegro's special feature is a high-ish level of code optimization, which can produce code that runs at about 1/4 the speed of C++. ''Depending on what the problem is it can be much faster, too.'' The standard commercial product is about eight thousand dollars, plus a runtime licensing fee. There are cheaper options if you don't want to compile standalone executeables, but you really have to dig at Allegro's sales staff or you'll never hear about them. If you do push and you don't need to distribute exes, you save about six thousand dollars a seat. If you need to run on Windows, do very thorough tests before committing to Allegro. If a Unix-only Lisp suits you, look at (the open source) CMUCL implementation. If you need a dynamic language with commercially guaranteed stability on multiple platforms, look at VAST, Cincom Smalltalk, and Erlang. Or use LispWorks, SBCL, or some other Common Lisp. From http://www.franz.com/ ''An emphasis for ACL 8.0 development has been on stability in multiprocessing environments. Testing is showing the stability of Allegro CL 8.0 equals or surpasses that of a fully updated Allegro CL 7.0.'' Beta-testing of Allegro CL 8.0 is now underway. See http://www.franz.com/products/allegrocl/ACL_8.0_beta.lhtml ( many supported OS's) See also: CommercialLispApplications