I looked at it but decided on the one level 6*2*2 from happyhutch for £120 (although you can get it cheaper from their ebay shop).
Thistle Hall is nice and deep and high, but by the time you've taken the hole into account on the top level, and the area of the ramp on the bottom level, it's not as big as you think and doesn't really give a lot of useable space to stretch out and move around. Personally I prefer the single level ones for this reason. I guess it depends on the size and shape of the space you have for it as well.