I own one for my 22.5" and it works pretty well. It can turn out some really great food. I eventually ditched the water pan for a larger foil loaf pan that sits on top of the center hole so I refill the water less. You can also run it fine without the water but the temps are less stable. Burn times vary and I find it works best to add charcoal every 2-3 hrs depending on the cook time.
Here's a link to a cook I did recently on it.
As many have mentioned, it isn't required to smoke successfully on the kettle. But since I have it, I use it every time because I leave it in all the time, there is no setup required. Just pour in coals/wood and go.
After about a year and a half of using it and learning, I decided to upgrade to a 22.5" WSM for more capacity and more stable temps.