I've been evaluating a bunch of them and the best one for price/performance I have found is EnterpriseArchitect : http://www.sparxsystems.com.au/Editions.htm
US$189 for professional version, though their business model is 12 months free upgrades and then what seems to be a resonable yearly subscription fee (I say reasonable because almost everyone seems to charge at least the same amount for upgrades after a year nowdays).
Tested it with a bunch of gnarly reverse engineer imports (java/C++) to check the model creation...excellent.
I have a couple of minor quibbles, but overall fantastic value, especially if you have been through the demo loop in search of the UML tool holy grail:-)
30 day demo plus also an interesting UML e-learning addon http://www.sparxsystems.com.au/zm/ZicomMentor.htm
Check it out for yourself.