McCLIM is and has always been a total mess (stability, look and feel, speed, platform support, feeling of robustness) and I would definitely not recommend it, at its current state, to non-hardcore Common Lispers (since it's likely to do more harm than good and turn people off CL entirely).

A big reason for that is its X dependency and focus on X/Linux as the prime development platform rather than a cross-platform base by default. Other projects (Pharo, Squeak, Factor IDE) have done a much better job at tackling similar issues.