I'm gonna guess that JRA in Medford has about the best demo fleet selection around if you live close to try some out.
Pedal Power in Acton has a 2012 Specialized 29'r Stumpjumper FSR Comp test bike (I think quite a few Spec. shops do so check) which I had for 3 days. 130mm travel F/B and I could immediately do things on that bike I can't on my converted 650B Prophet. Shocking really, so at least test out a 29'r to see how you like it. Personally I wouldn't purchase a 26" bike again for "all around use". 650B or 29'r. Like it or not the 650B size is now moving full steam ahead with 10+ manufacturers (I'm losing count) producing bikes along with plenty of new tire and rim choices.
3K will get you a very nice bike. 2103 bikes are rolling in now so look for 2012 or even 2011 leftovers. I found and purchased 2 leftover 2010 bikes for my son and daughter (Gary Fisher Roscoe 1 and Specialized Safire Comp) for 1/2 their original MSRP. Deals are out there.