I'm not sure that I take the paranoid view, but this is nothing but bad news for ArcSight customers from where I sit.  Any time you have heavily invested in an architecture and that architecture is absorbed by a new company, you are in for bad news.  Support is never the same.  HP is monolithic and generally slow to respond to company demands (and even notices of software vulnerabilities).  For an example of the latter, I know people who took the old 'BackTrack to the Max' course where Mutts presented his HPOV vulnerability for more than a year after disclosing it to HP without them doing a thing about it....

I mentioned McAffe in order to compare Mcafee -> Intel with Arcsight -> HP.

I found McAfee products pretty good, my only concern is the future of the company under Intel.