I don't know about the E8400, as I don't have one yet, but on paper it's extremely strong against the Abit IP35. In practice though, it's not really cutting the mustard across all the Intel CPUs like most P35 boards do. It overclocked very well with an E6750, but I can't get more than 3.4GHz stable out of a Q6600 that I know is good for 3.8GHz stable/4GHz SuperPi stable in a Gigabyte P35-DS4, and it's overclocking performance with E21x0 CPU's is also very patchy.
Unfortunately I think they've sold about 5 to a fairly varied group and the findings have been a bit sparse and/or not resoundingly positive. I can't help but think that if OcUK were serious about these boards they would have given out a few to hardcore overclockers and published the results. Or even got their own people in-house to put up some strong overclocks. The fact that they don't appear to have doen either of these would suggest to me that they either can't be bothered, or they've tried and the results weren't publishable if you get my drift,
I'd get the Abit at the moment, but the J&W staff are very responsive and a new BIOS has just been released. I'm not in the UK at the moment, but I'll be back early tomorow morning at which time I will try the new BIOS and post my results.