The 'issues' people have with valve amps i.e. maintaining them, new valves etc, is usually to do with an all-valve pre and power stage. The Terror just has a valve pre-amp so you'll be fine. Pre-amp valves last a lifetime, and you'll most likely only change them if you want to try out different types of gain.
I'm not entirely sure why the Terror has a standby, but as it isn't all-valve, I would imagine it's pretty useless.
That's not to say the Terror is in any way inferior. Great amps, and sounds a lot like my all-valve AD200...just about a third of the price!
Enjoy!