"There are so many reasons I love Yahoo..."4.5 stars
Pros: Stealth settings, so you can avoid some people while talking to others; built-in Internet radio; Yahoo Mail and Calendar notifications
Cons: Sometimes some of the IMVironments make my system sluggish
Summary: First of all, when you sign in, you can choose to sign in as invisible, meaning no one will know you're online - unless you want them to. (Quite useful for when I'm tired, and I just want to hop on to tell my boyfriend good night.)
Second of all, it has lots of bells and whistles. The ones I use the most are e-mail and calendar alerts. (When you get an e-mail, or have an upcoming event, it alerts you with a sound, a pop-up window, a status bar message, or a combination.)
I also love listening to the Internet radio, and challenging my friends to games. (You can play Pool, Scrabble, and a few other games in the same window that you chat in.)
Basically, the best part about Yahoo Messenger is that you can make it whatever you want. It's so customizable. All you have to do is change your preferences, and you have your own version that works just for you. (The preference box is easy to get to by pressing ctrl-shift-p. It takes a few minutes to go through and read all your options, but it's worth it.)
As far as support goes, I've never needed it. I had no problem with my install. (Although, for the record, it's helpful to select Custom install if you just want Messenger and nothing else.) Once it was installed, everything was pretty much self-explanatory.
I love Yahoo so much that I've recently uninstalled all my other chat programs. It's at least worth a try.