I'll go ahead and tell you my horror story. Bought my L25500 2.5 years ago, not one single problem the first year (besides printheads). Mid-august of this year, something strange happened in my take-up reel, which sent an electrical current shooting through the machine. Long story short, it ended up taking 8 weeks, and $4500 worth of parts (not to mention the labor) to get it running again. The reason it took so long, is because HP departmentalizes their parts department. It's divided into warranty, non-warranty and reseller departments (I may be wrong about what the departments are called etc but you get the point). What happens is that warranty folks are first in line. And they keep a certain stock of parts for warranty issues. Then if there's anything left, those parts go into the reseller dept. And then there's the non-warranty folks. One of the things I inquired about was a media jam sensor. $80 part. Was backordered until mid-november. I ended up having to import one from Canada and payed $350 total for it.
I don't know for certain, but I'm pretty confident if I had been under warranty, it would not have taken 8 weeks and it wouldn't have cost me a dime! (besides the cost of the warranty of course)
I run my machine 6-8 hours a day most of the time and I don't have time to tinker with it and try and fix it myself. And I certainly don't have 8 weeks to try and get it fixed.
These are very complex machines (more-so than I had previously thought) and there is a LOT that can go wrong, and the parts add up in a hurry!
I vote for buying the warranty and sleeping at night!