Ok, to be honest, I figured my next bike was going to be a Pivot Mach 5.7. I figured full suspension 29ers were just going to be too big, between stand over and ETT. Then I heard about the TX29er, and as luck would have it, our LBS hosted a demo.
I figured I'd be an xs. They unfortunately had none of them in that size to demo, but they did have an xs in the Anthem 29er. I swung a leg over and instantly felt the cockpit was too small. It felt awkward to me. They rolled the small TX 29 over and like Nicole said above, it just felt "right" to me. The spacers had been removed from under the stem and the stem was also flipped. The seat was adjusted and it's almost dead even with the bars. I rode it in the parking lot and it seemed fine, but who can really tell there?
I was able to test ride it on our local trail later. Right off I started on some rather tight and twisty single track that slowly climbs to the top of a ridge. There are lots of roots and I would struggle on my old bike. I rolled right over some areas that have always given me trouble and didn't feel like I had to manhandle or put a lot of effort in to finesse it through the trees. I was very surprised at how stable the bike was at slow speeds and how well it made its way through the tight, twisty stuff. I wasn't expecting that.
I made the climb much faster. Rather than struggle over the roots, the 29" wheels just rolled on over. It's going to sound cliche, but really, it was almost effortless. Dismounting and climbing back on was much easier than my old bike. There is a lot of great things to say about the components on this bike, but I'll skip that because you wanted to know more about transitioning from 26" wheels to 29" wheels.
After I got to the top of the first climb, I rode along a ridge on some fairly level terrain. Now, I've heard a lot about the bigger wheels taking a while to build up momentum and get going...but I honestly don't notice that on this bike. Then again, I wasn't concerned about being first out of the gate. BUT, I did notice how much they haul, and that bike hauled, when I hit the throttle a bit. And, I got my first taste of the term "flickable". This bike hopped over small stuff so easily and was just so maneuverable. Again, I was expecting to have to put more input into it, but I just didn't find this to be the case. I had been really excited to try the bike, and compare it to my dream bike (the Pivot).
Next step was to take it downhill. In a word? Inspiring. Rocky rough stuff with roots thrown in for fun that would throw my wheels around on my old bike just didn't seem to matter. It just wants to go over everything. I flew down the hill with the biggest grin on my face and knew this bike was going to be a serious contender. As luck would have it, my LBS was able to get me a fantastic deal on the small XO, and I jumped at the offer, and never looked back or second-guessed myself.
So, while my initial test ride was highly favorable, it's not the same as spending a lot more time in the saddle and really put it to the test (at least as much as I was able to, and I can say with confidence this bike can handle way more than I am currently comfortable dishing out). So, first group ride. Right away my friends noticed how much faster I climbed. I suck at climbing. This thing scampers. As we hummed along on the trail, we approached a log pile that has always been my nemesis. I decided to try it. I sailed right over it as if I had always done it. After that one, several more followed. I was elated. I had been so frustrated by my fear of going over stuff and having to constantly dismount. Besides the bigger wheels, I just felt so much more stable. And knowing I could dismount without coming down on the top tube, for me, was huge. I know a lot of people don't find standover as important, but the top tube on my old bike had been right "there" and I don't care if you are a woman, it still hurts!
Cornering, that's something else I'm starting to enjoy! I just didn't feel stable before, and like I couldn't really lean into the turn. I'd fight it. Much to my delight, when I hit my first banked turn, I leaned the bike over and felt what it was like to corner. The more I tried, the more I found I could do.
Descending. Between the bigger wheels and slacker head angle, pointing the bike downhill over rough and technical stuff is so much more fun. I'm able to move around in the cockpit easily. I feel like I'm riding in the bike, between the wheels, rather than perched on top of them. So, I don't feel too tall or top heavy.
So for me, this transition to a full suspension 29er has been confidence-boosting. This is totally been the bike for me, and I don't find myself regretting the decision to go to a 29er instead of a 26" bike. But, it's totally about your perception. I'm sure your wife may have read how others tried them and wouldn't give up their 26ers for anything. The majority of the trails I ride range from technical xc/trail. For me, this bike is perfect for that. It doesn't tire me out as much on longer rides. I find myself deliberately choosing harder lines. I think if xc and technical trails are what you are riding, a 29er could definitely be in the cards for her.
The bad? Honestly, for me, I can't come up with anything yet. I don't think I will. I sold my old bike and still have a hardtail 26er hanging out collecting dust. I have a singlespeed 29er I built up from the frame a couple of years ago, and that's used for pure xc stuff and winter riding. It's got a much more xc geometry and I wanted something with full suspension and with a more aggressive geometry. Between that and the larger wheels, this bike has been a game-changer for me. Would it be for your wife? Only she can decide that, but hopefully you'll get to try out some different bikes so she can see for herself. I didn't really feel like I had to transition; it felt natural and right.
So, this wasn't very quick, but there was so much to share. Hope this helped!