The nimbus is entry level, the KH is top of the line. The nimbus is strong and tough, the only issue people have with them is that the crown is quite wide and some people hit their knees on it. I wore through a set of 661s by rubbing them against the frame when i was hopping but i have fat legs so would still reccomend it.
I have heard of quite a few people hitting their knees on the frame, but I have only done it once.
I would of hit my knee no matter what frame I was using too, I just wrecked and landed with the knee going right into the frame, but I have never hit it from when im riding and jumping. Just from that one wreck. =p
For the strength and durability of the Nimbus II, and for how cheap it is. Its a great frame.
I also love the frame design, for foot-on-the-frame tricks, my foot feels like its bolted onto the frame. No slipping.
I use the Nimbus II 29" with a 700c x 35 Kenda Kross Supreme. Eventually I’ll put a 29x2.3 WTB Exiwolf on it to see how that handles and it would definitely fit a 3", but right now it’s just a commuter. It’s kind of a take it or leave it frame; nothing stands out or glares at you. It’s wide, but not too wide. Strong, but not bombproof-- I’d buy it again if I was looking in the $42 range.
It’s available from www.unicycle.com or any of their national subsiduaries. I’ve seen nimbus II frames used on freestyle, trial, muni and commuter unicycles. The bearing holders aren’t as fancy as the KH ones but they hold the bearings, they don’t break, I can’t see how you’d describe them as crappy, they just don’t look super fancy.