Highly recommend it. Much easier to keep a consistent temp without constant babysitting than an offset. It's not huge as far as cooking space (2 18" racks), but then again, it's a hell of a lot more portable than an offset too.
I love mine, but I also want to have a nice offset too. The WSM is the best $200 I've spent on a outdoor cooking.
I got one of these bad boys for Xmas and I've used it once -- smoked a whole chicken and a rack of ribs. What's the biggest brisket y'all have smoked in the WSM? I'm hoping to do one next weekend. Also, when adding more charcoal on longer smokes, do you fire it up in your chimney starter or just throw it on the already-burning coals?
I can usually dial in a steady ~225F, even on overnight cooks, using a larger replacement waterpan, and the 'Minion Method" (lit chimney of charcoal on top of unlit charcoal-- see the virtualweberbullet site). You can pick up a perfect fitting pan that is actually a Brinkman replacement- for $5 at BassPro. (I can't remember if Academy has them, think they may carry a slightly smaller Brinkman pan).
If you set things up right, your ~10lb brisket(s) should be done way before the fire needs more fuel (unless you have a monster brisket, or it's really cold outside). I've had temps still at 200+ after 14 hours before. If you run without a pan, or with an empty pan, you easily get in the ~350F range, which is a good temp for chicken and turkeys.
As for brisket size, I've always defaulted to ~10-11lb size, and just cooked two at a time if I needed more. Guess you could probably get ~15 on there, limitation is the footprint, as the smoker diameter may be close.
I have also removed the center section before, rearranged the grates, and cook steaks on top of the charcoal ring- which turned out great. Probably 600F plus.