I had a rim brake on the D2 rim, but this carbon rim has no braking surface so I had to take it off. I might put a disc on it (Got plenty of clearance to do so with a bit of grinding) but I’m pretty happy without, so might not bother and save myself the hassle 
Not a chance you’re stopping that thing quickly with 110mm cranks when at any reasonable cruising speed!
I can stop reasonably at ‘cruising speed’, it’s when you get to ‘racing speeds’ that it gets a bit dodgy. The lighter wheel stops even easier 
For me it’s just feeling confident that I can stop if something happens in front of me. Especially on a shared use path, if a child or dog or person ends up in front of me, stopping in more than about a meter is not really good enough. You can’t do that without a brake when your wheel circumference is multiple metres.
I probably wouldn’t be high gearing it (at least not at raggin’ it speed) in those situations anyway I never actually learned to stop with the brake either, just slow down big descents.
But even out of gear, or going slowly, half a wheel rotation is not going to be enough to stop a 29" wheel.
Speaking of light wheels, how does that thing handle at speed? Despite the weight criticism that 36" wheels attract I find my 36" much less fatiguing and tedious to ride compared to my 26" due to the weight/momentum difference. It feels like I have to pay much more attention to my balance point on the 26".
A 29" guni certainly has appeal since it’s compact and removes the mounting challenge of a 36", but I always wondered if it would be more fatiguing and less forgiving due to the lighter wheel.
Here’s an interesting feedback seen on FB about a Schlumpf hub in a 32":
To be honest, I haven’t riden it a lot in the last months but it is indeed a big difference to g29 (which I rode for almost 10 years before the g32) as it is a lot calmer. I am convinced that it is the ideal wheel size for women because it doesn’t need as much strength as the g36 (and you don’t fall as high)
I’m not a woman so I can’t comment on that part, but I do find the G29 tiring as I need way more focus when on it.
I’ll have to agree with this pierrox. I have no experience with geared unis, but my 32 was so much more stable compared to my 29, I ended up selling the 29.
I’ve never had trouble with that on any of my 29" wheels (of which I’ve had 3 now!) - I can ‘slam on’ from a cruising speed fairly easily. In high gear it’s harder but not impossible in an emergency!
As above - it’s squirmy. With the hub on the D2 rim, I eventually got used to it, so I’m sure I’ll get used to this one - it’s definitely harder to ride than a 36er but I find I get more fatigued mounting/dealing with traffic on the 36er than I do riding the g29 in a straight line, so it’s a good trade-off for me.
I have to admit I’ve not managed to ride the new carbon rim too much yet, I’ve got some weird knee injury I can’t quite shake. I’ve done a few very short (sub 2 mile) rides and love how it feels, but I’ll reserve a ‘real’ review for when I’ve done 20+ miles in one sitting
Made a bit of a whacky upgrade to my Guni - I’ve painted it in reflective paint, then covered THAT coat up with some clear, but refractive tape. So now my uni has some very reflective rainbow bands round the legs. You can see the un-taped reflective paint at the fork crown glowing very brightly white, the tape seems to have dulled the effect a bit but it’s still plenty visible to a bike light!
