I've split the beech handle on my 1/2" RI. Made a new one of hickory, hasn't busted yet (and it's a lot more substantial than the beech one that came on it). Of course, keep in mind that I mortise with a mallet that's probably about 4 pounds and I like working with harder woods like hickory.
They are a PITA to sharpen as well. The first 1/2" I had chipped like crazy and constantly needed re-sharpened; it was also not straight. It was more dog-legged. The replacement that TFWW sent me as well as the 1/4" I got work wonderfully, though.
The Barefoot Woodworker.
Fueled by leather, chrome, and thunder.