Hardware defects are never really funny - but you anyway have to handle them and get the machine back to "normal" as soon as possible.
The declaration of "asap" is very different, depending on which company you're dealing with. In the last couple days I've had two different support cases, one with SUN and one with DELL - and hell! What a difference!
I've opened the case with SUN on November 6th, gave information about the serial number and type of the server, described the problem (hardware fault) and delivered the Linux kernel logs describing the crash. I had to wait 10 (!!!!) days to get an answer saying I have to upgrade the BIOS and other hardware firmwares. I did as said the following day with the same result: Server crashes. And since then I'm again waiting for a response.
The second case concerns DELL. My Nagios plugin (check_equallogic, soon generally available) detected a Disk failure. I confirmed this on the Group Manager and really, a disk was showing status failed. I've opened a support case this morning at 9:17am and guess when the disk was replaced and case 100% solved? A few minutes ago at 12:38pm.
To make it a bit more fair, I have to say, that the DELL support is a 4h contract and the SUN support is a Next Business Day contract, but still - I guess you can imagine how much time it should take to solve a problem, even with a Next Business Day case.