One of the very nice things I noticed about it last night was the hub is completely silent. Like a clutch-less police hub, no click clack when coasting, just dead silence.
For those who are using XtraCycles or other work bikes this seems like it's going to be a robust hub that can withstand the rigors of the extra loads.

Except for its size this hub has impressed me as much as my Rohloff.

Interesting...

Does the gear range compare to the Rohloff?

No. The Rohloff has a sizably larger gear range. ~500% vs. ~300%. The NuVinci gear range is comparable to the 8 speed hubs (Nexus, S-A, and the like) though.
On my Salsa with the Rohloff I have a 52 tooth chainring and a 16 tooth cog
Gear Inches from top to bottom are:
125.3
110.3
96.9
85.4
75.2
66.1
58.2
51.2
45.1
39.6
34.9
30.7
27.0
23.8

On the XtraCycle with the NuVinci gear inches range between 32.6 and 114.2 inches, 42 tooth front ring and a 16 tooth cog.

How do they perform at -30C ?

I'm in the Deep South (Georgia), so I can't say. It does work very well at 93ºF and 85% humidity.;)

Well, the efficiency of nuVinci is not that great look on thread http://www.bikeforums.net/showthread...=304869&page=3 where I posted my findings.

AllenG, What are you using for a chain tensioner here? I am trying to install a NuVinci on my Xtracycle but I've found that the shifter mechanism doesn't leave enough room for a derailleur or a Surly singleator.

Thanks.

That's a Rohloff chain tensioner. QBP now carries Rohloff, so you should be able to get one through your LBS. If not, below is the Rohloff USA distributer listed on their website.
You may also want to look at On-One's Doofer. I use one of those on my Salsa La Raza and it has a lot of adjustment travel.

Thanks for the info Allen. I ended up rigging up a simple extension plate to make room for my surly singleator chain tensioner. This has been working great for me, though I had to switch the spring in my chain tensioner so that it would push up; when I had it pushing down (as shown in the first pic below), the chain would skip under load. No problems with the singleator pushing up. I have the chain on the smallest chainring (28T) of my old triple up front. This gives me a lowest gear that is low enough to spin up the ridiculous hill to get to my house, and a high gear where i can still feel resistance from the pedals going downhill at 25mph.

Overall, I have been very pleased with the nuvinci hub. It is a delightful sensation to be able to change gears with no clicks or sudden jerks. The only major downside is the weight, but I'm not building this xtracycle up to be a speed demon anyway :) I have also noticed that shifting under heavy load is very difficult if you don't let up on the pedals a bit. This hasn't been a problem for me either since I prefer to keep my cadence fairly high.

Extension plate with chain tensioner pushing down
http://lh3.google.com/emeldebug/RsCV...8/PIC-0041.jpg

With chain tensioner pushing up
http://lh3.google.com/emeldebug/RsCV...8/PIC-0047.jpg