I did it in August. Bought my 29er frame and 29er forks from the states for far cheaper than i could get them here at the time.
Heard plenty of stories telling me i shouldn't but i found the whole thing very easy.
Frame was £1400 here, forks £550. I ended up paying around £1200 all in so very definately worth it. Postage was £56 and duty was £113 (both included in the £1200). The key is to get the seller to declare his cost amount for the frame, not what you actually pay for it so the duty charged is lower. Not all people will do this so check first.
Also bought another set of forks recently and again found it very easy (as long as you can cope with the extra wait).
The one downside is warranty claims i suppose but for me the £750 saving was more than enough to take the risk.