I've been running this for a few days having upgraded from whatever the latest pre-version-5 version of the OS was. I find the device more responsive generally. I like the updates to the UI and the icons (e.g., my BES mailbox now also appears separately from the main Messages folder.
I am not a very heavy user apart from email and some browsing now and then, but I haven't had any problems. I find I can get several days on a charge.
MUST - the independent Manchester United supporters' trust - www.joinMUST.org