yeah i looked at the wilma and (very briefly) the betty, but Betty was too expensive, and the wilma shots + reviews i read didnt seem to rate it much better than the tesla which was quite a bit cheaper. Another one to consider would be an Iblaast from New Zealand then a battery from a guy called Smudge who posts on here sometimes and on STW as 5mudge (i think) he's from the UK, and will do a decent 4.4Ah battery + charger for about £100 delivered. Does 2.2Ah as well. But i didnt like the bar mount on the Iblaast and wanted something that would work out the box with no faffing.
You could always order a tesla and just play with it to see what the beams like on some dark track. Thats what i did with the tesla, just took it to a nearby bridleway in the car the day it arrived and had a look at the beam. I was impressed with it though so kept it. I think the tigerlights bloke might have a demo light if you email him as some bloke on STW mentioned he'd used a demo one for a bit. I guess you might have to pay postage if you didnt buy one, but at least you could have a look. They look impressive, but i wanted a longer run time and a Li-ion battery not a lipo one.
If you get a tesla, it fits an oversize diameter bar straight out the box, just need to stretch the fastening band a bit more.
EDIT:
I think the reason the tesla is getting good reviews is the reflector design. Although its down a bit on lumens compared to the wilma, and (on paper) the Lumicycle or tiger lights, the actual spread of light (nice pool of light by the wheel, but also a good penetrating beam further out) makes it so good. Have a look here for the beam shape... (scroll down the page a bit, and open the images in different windows / tabs for a large view comparison)
http://acidinmylegs.blogspot.com/