I'm going with Magma's new detachable pedestal.
This one. 
I'm installing it under the starboard side locker on the swim platform of our 348. That way there won't be anything to stub toes or trip feet. The pedestal base they supply is pretty low-profile and all edges to it are rounded. It's about as low as can be made without having a hole through the decking for a post. I'll post pix when I get it done (probably next week?)
I've seen others put the base in the same cavity as the stored swim platform ladder. I'm not sure that's something I'd do. If you block the ladder you can't get back onboard. Accidents happen. Or even if people are swimming (as my wife likes to do) on the run-up to dinner being ready. Block the ladder with a hot grille? Not quite what I'd consider a good idea. I know it's tempting to do it to avoid the mount being in the way. But I'd rather have that than lose the use of the ladder. For the swim platforms that are just a "shelf" I'd go with the recessed pedestal mount instead (like how the cockpit table is mounted). In that situation you're not dealing with a big through-hull into the boat, as would be required on the 348.
We've grilled the past two seasons on the boat and it's been great. The Magma grill cools down pretty quick. By the time dinner's over it's nearly cool enough to stow back in a duffel bag I use for it (medium sized one from REI). That and the bottle gets stored in the swim platform locker, not below, to avoid any possibility of propane leaks. A $3 coleman can of propane lasts us a whole summer. I probably would not use charcoal on a boat as there's no easy way to deal with the embers. Tossing them overboard is not legal in most places and why would I want the hassle of going ashore to bury or otherwise dispose of them?
The only thing I avoid cooking is hamburgers as the grease from them tends to drip. I've had the grill on the stern rail of our 348. I put a rod holder on the rail (canted to the starboard side about 45 degrees) and use the Magma rod holder gimbal mount. It has worked well enough except for the dripping issue. The transom slopes outward under the grille and any drips mean more cleanup and re-waxing. Thus I've avoided things likely to drip. Strip steaks are our most popular dinner, along with corn on the cob cooked right in the husk. Hopefully by using the new pedestal location I'll be less concerned about possible drips and get some burgers going this season.