"Hank Hill gives up propane and buys a WSM!" If that's not the ultimate endorsement, I don't know what is! (Sorry for the horrible King of the Hill joke, but it had to be done.)
My first couple cooks were pork butts. I knew I'd be going through a bit of learning curve with regards to temp control, so I wanted a fairly inexpensive cut of meat that was fairly forgiving to inconsistent temps. Ribs were my third cook. Everything turned out great. After about 6 cooks, the inside of my WSM was fully "gunkified". This must have been the final step needed to seal things up because my temps became much more stable. Just another heads up, if you're anything like me, plan on being disappointed with your first brisket. It took me about three attmepts before I got what I would call "good" results.
Lastly, the only mod's I've done are: Thermometer in lid ($14 at Wal Mart), a couple handles mounted in the mid-section, and I replaced the Weber water pan with a larger Brinkman pan and a 12 inch clay saucer. Again, congrats on the WSM and welcome aboard!