If you're over 6' they feel more normalized based on the trend of having manufacturers build frames that place the rider on top of the bike. If you're on a slopped top-tube bike, it feels big.

They're great for straight, bumpy conditions; where they tend to fail is sketchy switch backs. I've had them wash out hard in conditions my 26" doesn't seem to have many issues.

For me, personally, I like a 29er simply because you can swap out 2-3 sets of wheels between a variety of bikes if you are using all SS/FG frames/builds. This means I can put meatier tires on my commuter (Handsome Devil) and swap back to 25c/28c without having to worry about going down to a 26".

the 650B (27.5") is yet another size deal that's been around for ever. I think the problem for most people is that these wheelsets make sense on a size of the rider basis, not on a what's hot economically one.