I have to go with Brian on this.  One company I know is running around 20,000 SuperMicro servers, and very few fail anything but a hot-swap hard drive.
The various components are bolt-standard, but the motherboards and chassis's are custom engineered.
SuperMicro custom designs their motherboards and chassis's; hundreds of other vendors whitebox the SuperMicro servers.

Brian Cluff wrote:
> I prefer to pay per incident, especially when using SuperMicro servers.
>  I've only used about 150 of them, but I have never had a single
> incident with any of them other than 1 that was dead on arrival due to
> some miss handling by the shipping company.  They have quite literally
> been turn them on and forget them.
> 
> Brian Cluff
> 
> On 08/21/2010 02:18 PM, Stephen wrote:
>> For me it it would be self built. But for a client where i may or may
>> not be supporting it would be a dell with the support contract.