It seems very solid. It pretty much overclocks itself actually. Literally all I had to do was lock the PCIe bus and turn up the FSB to 360 to get 3.2GHz on a Q6600 G0. There is practically no Vdroop at all and the P35 chipset itself is very fast and stable. I'm having a bit of trouble getting my known-good-for 3.8GHz CPU over 3.6GHz, but I think that's just down to my not being experienced enough with the chipset adjustments.
My father, who was a 'proper' electronics engineer reckons the quality of the motherboard itself is very good and any components used are brand names that most people would recognise from any other motherboards.
The chipset cooling is also a revelation as, despite having a tiny Northbridge cooler, and nothing at all on the VRM, it runs REALLY cool, maybe luke-warm to the touch, which is the coolest of any of the P35 boards I've seen yet.
The only issue I have found is that the implemenation of ICH9 seems to be locked into UDMA5 (ATA-100) which limits maximum data rates at 100Mb/s which is well short of SATA I (150Mb/s theoretical) or even UDMA6 (ATA-133). This is disappointing as the board claims SATA II (300Mb/s). I think it should be possible to address this in a BIOS update as ICH9 is definitely SATA II capable, as well as AHCI, hot-plug and NCQ, none of which are currently available on the OcUK IP35-Pro.