Hm my experiences are mostly negative. Their phone support / sales is particularly bad at times. A friend of mine ordered a case, and then a motherboard, cpu, and memory combination. The case arrived within a week, but the other three items didn't arrive. He called up and they said there was a problem with the credit card... why didn't they call him and report the problem? He finally got the mb+cpu+memory after several phone calls (at the time their phone system was so screwed up that he was on hold for 1 hour and then got transferred to a non-working voicemail box). The memory was bad and ended up screwing up his registry. This wouldn't be all that bad were it not for the fact that they claimed several times on the phone that they test the parts thoroughly before shipping. Yet when we enabled the full memory test on POST, it failed. He called them back and they didn't even offer any apologies or compensation for all the troubles he had gone through.
Another friend (my roommate) ordered from them recently. His stuff was late so he called up and they said that due to an error his order got screwed up but they were shipping it soon. He checked it again later and they were no longer getting the CPU he had ordered (and had sold out of the current stock). They "offered" to let him pay more for a more expensive CPU. Finally they agreed to upgrade his processor for no charge. He then ordered a case from them, which arrived with no manual (although the case is supposed to come with one -- I know because I ordered the same one from onvia and it came with one). He called them three times to get the manual and never did get one. Finally he talked to the manufacturer (Antec) and they sent him the manual.
Those are the two "major" experiences I know of. Other friends have ordered and had minor trouble with their phone support (they seem to only be around about 2 hours in the day, although their sales people are around for extended periods). I myself ordered a stick of RAM and didn't have any troubles.