i ran 4600mhz benches, 4200mhz stable 24/7, 4730mhz validated, 4500mhz prime, 4400mhz in crysis on my ip35-e with an e8400
edit: pretty much anything above 4.2 failed. Stability can be found anywhere from 4.0-4.4 depending on your cooling and (I've seen 4.5 9+hours of prime now as well). It's possible to run super high like 4.6g-6.0g for suicide benches, but you'll need insane fsbs, water/dice/ln2/phase cooling etc, dangerous vcore, and an excellent mobo/ram for that. an ip35-e will do about 520mhz if you're lucky, and not with a quad, only a dual. (maybe quads if you're an expert)
also: my ip35e didn't work out of the box on 45nm until i flashed the bios using an e2140