I've only ever used HP for low end and non critical stuff (iLo networks and the like), reason being that when you get to high end gear you're usually using high end features or fancy architecture and virtually every vendor has unresolved bugs in the fancy features, that goes for Cisco, Brocade and even Juniper. The difference is the competance and ability of their TAC and dev teams to fix those quickly, I don't believe HP have the resources available to play that game as well (even in the high end network vendors, Cisco and Juniper are a cut above everyone else in the their fix times and general ability).
Things will break, it's how your vendor deals with it when it happens which matters. HP do simple stuff OK where not much goes wrong (because they haven't added anything new for 5+ years you might argue) but I don't trust them for the big stuff or actually for the small stuff where it matters to be honest.
Cisco had an issue with flexlinks leaking traffic a while back in a specific IOS version with certain conditions. That's not a complex feature really but it took them a day or two to track it down given the diagnostics, when they did we got a fix pretty quickly. Juniper are super quick to fix their bugs and issue revised code, Brocade are slower but do get there. Lower end vendors tend to spend a week insisting it's something you're doing wrong before even looking at their own code, that's not a game I'm willing to play.
