I actually tried a 700c conversion recently with a '94 Stumpjumper I had. It was not what I would consider to be a success, however - for all the reasons mentioned above.

The bottom bracket is up too high, and as a result the bike is a little unstable. Handling is pretty weird. I realize that IRD used to build Stroker ATBs for difficult applications, and that those bikes had huge ground clearance, but they also languished in the market. If you aren't climbing logs all the time, the stability and stand-over issues are a deal-breaker.

The rear brake conversion went off without much of a hitch, but I eventually just broke down and bought a used Trek XO-1 for cross-duty. The Stumpy will be converted back to 26 and will be relegated to downhill park duty this summer.