I was able to put the SB5+ through the paces for 3 days during a trip to Summit County, CO this fall. I've had the SB5 in the past, and presently have SB4.5 in the garage, so it's safe to say I'm a disciple of the Switch Infinity linkage suspension. The SB5+ follows in the same vein as the other bike of the SB lineup with incredible pedaling efficiency and power transfer paired with a supple, bottomless, feel once things get pointed downhill.
I didn't have a scale with me, I'd put the Yeti's claimed weight of 28lbs without pedals as being pretty accurate. My SB45 weights 26.5 with Enve wheels/pedals, and the SB5+ didn't feel much heavier in hand, or riding on the trail. The benefits of plus tires proved true, with confidence inspiring grip in loose conditions, and forgiving float over chunk rock gardens. I was tentative about flatting, so I ran what I felt was a higher than normal pressure of 15/16 PSI F/R for my 140lb frame, and had no punctures to speak of, so credit to the Maxxis Rekons there. My biggest day was a ride over the Ten Mile Range from Copper Mtn ski area into the town of Frisco. Going up, the plus tires had grip for days, and if I had the capacity to turn the pedals, the bike would have kept going, but damn did it get steep! Once on top, and coming down through the scree and roots and rocks, the SB5+ only inspired more and more confidence.
The last day I decided to experiment, and moved my 29" Enve M60 boost wheels onto the SB5+, clearance was a non-issue on both the rear triangle, and the 27.5+ Boost Fox fork (photo'd below). Ride wise the bikes geo wasn't adversely affected, and I didn't notice and difference in steering or feel. The most noticeable thing was the reduced wheel weight going from an alloy 27.5+ setup to a carbon 29" setup with 2.35 tires. I charged down the last part of the descent I had ridden the previous day on the 27.5+ wheels with the same confidence and speed. BB height on the stock SB5+ is on the lower end at 13", and I did notice more rock strikes initially, but never felt it was a constant problem. Overall I came away very impressed with the SB5+, I don't race regularly any longer, but still like a fast, capable bike. Should the occasional race pop up, I'd have no problem calling the 29" wheels into duty.