HP's desktops and laptops suck bigtime, but their enterprise equipment is just as good as it's always been, and so is the support. Given that you're looking for managed switches, though, and are already a Cisco shop, I would probably stay with Cisco unless I was replacing everything. Saving a few thousand bucks on switches when the potential for tens of thousands in problems exists (interop, staff training, etc) further down the line doesn't strike me as the best idea.
That said, we're a (very small) HP shop, and here are my thoughts:
Price: As far as price/featureset goes, Procurves are probably the best bang for the buck (IMHO.) They cost more than your low end guys (but then again, who buys D-Link and Netgear for a real network?) but are almost always significantly less expensive than Cisco, Nortel, etc.
Reliability: Very good. Not bulletproof, but definitely top tier gear. In five years, I've had a switch engine go flaky (still working, but starting to produce bad diag info) and a power supply (on a different switch) fail.
Ease of use: The web interface is fairly nice, if slow (java) and covers most tasks. The CLI is straightforward and covers the rest.
Support: Procurve gear is waranted forever. If anything ever happens to your switch, HP will have another one there by 10:00AM the next business day (no cost on shipping either direction.) I've never seen (or heard of) hold times greater than thirty seconds. Techs actually speak english, as they are located in Colorado.
Anecdote: last year, one of my 4000Ms (we use them as a core switches--hey, I said we were a small shop) that covers my manufacturing shop died (the previously mentioned power supply failure) at about 4:00PM on the Friday before 4th of July weekend. Just about everyone at our site had gone home early (including me) and no major troubleshooting was possible with the personnel remaining. Because of the holiday weekend, if a part didn't ship on 7/1, the earliest we could expect a replacement was wednesday, 7/6. If it did ship on 7/1, it wouldn't arrive until after start of business on 7/5. I called HP Support from my house, got a tech who took ownership of the case and worked with me, and, without more than the simplest of troubleshooting (there was no one there to do it) or even a serial number (the switch was in a hard to reach area, and no SN could be read unless and until the switch was dismounted) shipped an entire unit (chassis, power supply, engine, and cards) to me with Saturday delivery.
The net result was that, other than the initial downtime on Friday, we didn't lose any manufacturing time. That's pretty good support (especially for a product that we purchased over five years previously) and cemented us as an HP customer--at least for networking gear.
