I have used the Community Edition and I found Poseidon to be a very easy to use tool. You can download the free version at: Poseidon UML My suggestion is try as many of the free products as you can and find the ones that are intuitive to you. From what I have seen, there are no perfect UML tools but if you test enough, you will find one that suits your needs.
I've used it here too. I try to get my guys to use this stuff but its tough teaching them. I didn't see the usefulness when I first started my career but after working with a Rational partnered company for 2 years it was the best thing I could have done.
I tried it for a short time, but I found it to be too restrictive. I prefer something more MS-Visio like...
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus