Mac Pro 2006 1,1 logic board failure after 16 months. Had AppleCare and after nearly 2 months of trying to fix the issue, Apple customer relations stepped in and gave me a brand new Mac Pro 2008. That machine functioned flawlessly until 2 original 1GB RAM modules failed a few months prior to AppleCare running out in Feb 2011. Not only did Apple replace the two modules, but for good measure they also replaced the riser card. No issues since then.
I use my MP for my business so for me, it's up time is mission critical even if I have a 2011 MBP that I can fall back on. Not having AppleCare is an issue but the MP is still blazing fast and has tons of life left in it. I go back and forth on replacing it especially since pricing has increased so much in the last few years. Nevertheless, depending on how business lines up for next year, a new MP could be in the cards.