As a disclaimer, I've seen the movie 5-6 times in the last 15 years, and I only just saw the musical this week. This allowed me to judge the movie without being tainted by what was or wasn't in the musical (however, it tainted me when I watched the musical :) )

I actually believe Michael Douglas worked quite well in that role, along with Kasey. I think her 'Let me dance for you scene' is one of the best parts of the movie, a worthwhile addition compared to the musical. The dancers and singing in the movie are much superior to the musical, as well as the cast which is at least 10 times bigger (easier to do in the movie of course). The decors, lighting, dancing, and singing are also much superior in the movie, which should be expected, and was indeed delivered.

The songs that were in common with the musical are better done in the movie, the new ones are quite good ones, and the whole movie just delivers more than the musical in my opinion, especially compared to a musical which has few decors. The one bad point on the movie is the obvious cuts between the actors talking, and dubbed singers during the singing portions for some of the characters, but their dancing is impeccable, and the end product was more enjoyable than the musical