1. No OS (Adds about £100 to the price if you were to put on a legitimate copy)
2. Lists onboard graphics - A card good enough to roll alongside an i7 2600 is going to be nigh on £200
3. Only 1333MHz - Sandy Bridge chips can make good use of up to 2200MHz RAM
4. Crap case
5. Doesn't specify the board model, only that it's a Gigabyte. There's a good chance it could be a POS. Risk not worth taking, even for a little over 4 bills.
Once you've added the necessary bits they've left out, you could have built one to your own spec, without the ailment of 1333MHz RAM or a possibly shitty motherboard. and since it's an eBay dealer who either imports or build themselves, who knows where they get the parts from (possibly rebfurbs or factory seconds?). Good feedback is an indication he's probably quite honest - but most of his customers might be clueless - so who knows. I've personally had little but bad experiences with eBay dealers like this.