I come from an all Dell Shop. The Poweredge Servers were good. Other than a couple of harddrive replacements, I had no real issues. One server did die on me but it was 5 years old and I beleive the cause was because of the air conditioning problem we had shortly before the failure. Both processors went on it and the warrenty was up so we retired it. We were slated for new virtual servers anyways, which are all Dell.
I have had more problems in the last few months on the new job because of HP Servers, than I did in 8 years of Dell Servers.