Okay, time to chime in on the "Pro-Water" side, not that it's "better" or "right or wrong", but I think that absolutes are being thrown around that are based on perspective, and there are alternative views of the "facts".
1. Simplicity. I like a "simple" process when smoking. That does not include various foilings, unfoilings, refoilings, pan-boltings, clay pot purchase/maintenance/storage, etc.
The water pan is a VERY simple tool and it works. I fill it with water, it gets dirty, I clean it out like any dirty pan. It is also a VERY good temperature moderator - Weber DID know what they were doing, and HOW to use their smoker, and although I understand it's fun to tinker around with things (hot rodding is an unavoidable instinct, I think!), but you are not going to "improve" upon Weber's basic design, only modify it to meet/need different requirements than the original execution.
When I go to smoke, I only need four things, the WSM, some charcoal/smokewood, some tinder, and some water. (and the meat of course!) No blowers, no flamethrowers, no foil, no claypots, no extra racks, etc. I did tinker around with remote thermometers a bit at first, but now I tend to "set it and forget it". The WSM HOLDS ITS TEMPERATURE - It really does! See cause of temp swings (minor at they are)
I like to smoke meat and be done with it. And if we ever have to move, or deal with an unsavory social disaster or something, and need to cook without utilities, my smoker only needs charcoal and water. Nice and simple.
2. Clean Up. "Clean Up". Yes, if you want to keep it spotless, you will not like cleaning greasy water and burned drippings out of it. But my WSM is a tool, not a showpiece. I clean the food grime off the grilles, the worst gunk off the water pan, and I hose off the main body once in a while. Yup, my WSM is starting to look a little like a mine locomotive in an Peruvian Copper mine, but so what? It works fine, and a little grunge actually helps seal the various joints - a win for me on fuel economy, but see "who cares" below.
3. Refills. The standard water pan probably does need a refill during the really long 12+ hour cooks. I don't know, I got a Brinkmann Charcoal pan to substitute for the Weber water pan, and I NEVER refill it. In fact, on some long cooks, it looks like it's nearly full when I'm done. Probably an illusion as it fills up some with grease and such, but I never come close to needing a refill at all.
4. Fuel Economy. Fuel economy. Yes, other methods may save some fuel, but who cares? We're talking about a few dollars of charcoal here, for cooking events that happen maybe 2-4 times a month? If you're more hardcore than that, then maybe fuel cost is an issue, but charcoal and hardwood is such a small factor in life's costs that it can be totally ignored. If you want to smoke food, you have to buy meat and fuel, and seasonings/sauce ingredients. There are plenty of "hobbies" that cost a lot more, and they don't provide you your daily meal as a benefit! Unless you're running a catering business, the cost of fuel is a non-factor. If charcoal is such a hardship, then use your kitchen oven, and roast your meat, don't smoke it.
5. Temperature swings/spikes. The WSM was DESIGNED to provide a very contained/consistent temperature environment. If you let the fuel burn down to even coals, (or set up a "Minion" style burn) temperature variations are VERY SLOW to occur. If you're getting a huge ramp up in temperature, than you're starting the cook too early, and need to let the fuel settle down, it really is that simple.
Once the fuel settles in, it's nearly impossible to get a dramatic temperature "runaway". Any gradual rises are easily handled by the air vents. I have actually found occasionally that keeping the temperature UP is usually a problem more often than an upward spike.
Also, meats are not THAT sensitive to 50 degree or more temperature swings. It's just meat, not some kind of pastry or delicate sauce. If the temperature moves, adjust your time, check the meat, cover it up, whatever. Ultimately it will be done according to texture, and that can occur at a nearly infinite range of time and temperature settings.
The water pan does a GREAT job of helping regulate the temperature though, during both a fuel "burn in" and during regular operations.
All in all, I find the WSM to be a very high quality, consistent-temperature smoker when used as designed, and I don't find any of the arguments against using the water pan with water in very compelling yet. Every one of them seems to be secondary or counter-productive to achieving a simple, delicious smoked meat product. But to each his own - people have different requirements for different reasons, and that's fine.
Other than increasing the size of the water pan (which I'm not so sure is necesssary for most cooks), I think the water pan design is great and is yet to be replaced by anything "better", just different - and that's cool too.
