Just been offered the update this morning and not quite sure if I want to update as I did on my nexus 7 and it made it quite sluggish.

Anyone else been offered the update and done it and if so how does it run?

I did my m8 about a month ago and had no issues at all, Improved battery life and made everything faster and more slick

There is a lot of opinion that Lollipop hasn't turned out to be the energy saver that was proposed. Maybe HTC has managed to make it work better for them. A lot of Samsung phones are struggling with piss poor battery life as a result of upgrade to Android 5.0. I put it on my handset last weekend (Note 4) I was losing 10% every 20 minutes or so, went back to KK in the end.

Its rather telling that Google is in the process of releasing 5.1 to apparently fix certain bugs and showstoppers, suggesting all is not well with the OS.

I'd hold off for a while: Lollipop is rather buggy.

I have to agree there.....though strangely on my Nexus 7 Wi-Fi (2013) it seems to be ok actually standby time has improved immeasurably. Running time seems to be better as well.

There's quite a serious memory leak problem that may have been fixed now but it meant that the battery life was really bad (as I recall).

In fact, Lollipop has made the battery life on most phones worse, not better as was Google's intention.

I think the memory leak is still in 5.0.2 but fixed in 5.1 but I agree totally on the battery life, my N5 has just lost the plot, somedays it's OK in the 6 hour SOT range others it's 2 and a half, upsetting really when I realise that my 6+ goes comfortably for about 14 hours of usage on 8.3 beta 2. Not to mention the encryption fiasco on the N6.

Project Volta hasn't really worked in reality, but I seem to recall that battery was one of the things tabled for 5.1 so hopefully they'll get it right this time, although I seem to recall that all Volta was was Job Scheduling and a battery saver mode but ART should have helped a lot.

Edit: OK upsetting's a bit strong, I meant disappointing

Well I updated last night and all good so far. It however took nearly an hour to update and it stuck at the htc one screen for around 15 mins which made me think id bricked my phone.