I used to use my Ranch Kettle for smoking all the time. It worked great! No problems whatsoever. However; I recently bought a new 26.75 kettle to do all my smoking because I found that the only downfall to smoking on a Ranch Kettle is that you have to keep adjusting three vents to maintain temperature. The Ranch Kettle does a good job of maintaining steady temps, but you still have to adjust the vents regularly.
I switched to a new 26.75 kettle for all my smoking because it has a one touch vent control and an ash sweep and bucket which the Ranch does not. On the 26.75 kettle, I placed marks on the ash bucket ring directly above the sweep lever to mark the precise location where the vents are completely open, 1/2 closed, and completely closed. It is so much easier and convenient to be able to slide a single lever rather than reaching up underneath a scorching hot cooker and having to touch three hot air vents, (burning my fingers in the process).
The Ranch is great for smoking, but the 26.75 kettle is better. The only advantage the Ranch has over a 26" kettle is its larger size and ability to smoke more meat.