I had a Wilderness Energy BL-36 - I bought their refurbished kit as well.
I was impressed with the kit - when it arrived it definitely didn't look refurbished at all. Definitely the batteries and battery bag were brand new (either that or their previous owner rode his bicycle indoors or something - there were no marks, dust or dirt on any of it).
I put it on an ancient cheap Specialized mountain bike that I had - it was a steel frame and was old enough that it didn't have shocks of any kind on it.
I rode the kit to work and everything was fine. Top speed without pedalling was about 18mph, pedalling a bit, it was more like 20-21mph.
Despite the fact that I liked the kit well enough, I almost immediately started modifying. I added another battery and went to 48V - top-speed jumped to about 24mph, 26-ish when pedalling. But then I worried about the controller getting destroyed or something due to the voltage and replaced it with an instant-start Crystalyte 36-72V 20A controller. The BL-36 kit that I got had the hall-sensor plugs and I took a chance that they were functional... and they were. I liked instant-start a lot more, but within a week or so of flying around at 48V with instant-start, I gunned it coming out of a stoplight and the motor just fell out of the front drop-outs. The drop-outs were bent pretty badly. I tried to fix the bike, but I couldn't unbend the dropouts - and I worried about metal fatigue. So I ended up buying a new bicycle, replaced the BL-36 kit with a Crystalyte 5304 (this whole e-bike hobby thing can get a bit addictive by the way). And then I sold the kit to a gentleman down in Denver who, last I heard was using it with great success commuting down there.
So, my suggestion - the BL-36 is a good kit. It's solid, well-made, and the refurbished kit in my experience was virtually the same as new. The torque is good - better than a 5304 at 36V. Top speed is ok - about 20mph. The SLA batteries are heavy (of course), but the bag is fairly well made, but it's a very snug fit with the batteries and the zipper broke eventually. The charger is good - although mine didn't like charging at in my hot garage (but worked fine when I took it into my cooler house).
I think it's fine on a good steel fork - even with shocks. With a pedal first controller, the motor doesn't pull as much as it does with an instant-start in my experience. I have my Crystalyte 5304 at 44V on an instant-start on a cheap Columbia Trailhead ( http://www.dickssportinggoods.com/sm-buy-the-columbia-trailhead-sport-mountain-bike-on-wwwdickssportinggoodscom--pi-2435910.html ) and it's been fine for over 1000 miles so far. Not that my one example is a testament to the safety of the whole thing, but so far I've been ok. I wouldn't hook one up to an aluminum fork - steel bends, but aluminum breaks.
Edit: I noticed after writing the above that this is the 35A controller. I had the 20A WE BL-36 - the 35A should have a fair bit more torque (almost twice as much, one would guess). If I bent the forks on mine at 20A, then at 35A, I guess there's a much higher likelihood of it being a problem. I tend to agree with everyone who says that you should be careful regarding the forks. I think it will work ok, but check them periodically, and I wouldn't recommend going off-road without a torque arm. And you may want to purchase a separate torque arm - like the one from powereridestore.com.
