Hmm.. well I wouldn't mind getting the IP35-E but I am nervous about all the "double booting" issues people have complained about. Not sure if that is fixed yet or what..
it overclocks a tiny bit better than a p35-ds3l, but theres no way your getting 4.0ghz without aircooling... because the max i've seen on the ip35-e was a 3.7ghz... but don't get your hopes on getting that high... each e2180 has their own way of overclocking