The XTAR is an excellent charger, the trickle level is about 0.1 mA, while the disconnected discharge rate is only 0.5 mA, both really tiny.
I'm using the timer because of where and how I charge. It's to protect against a charger failure, including if we get a surge on the AC power line (rare, but it does happen), and save power (the timer draws no power when in the off state). I went for a full year with the basic TR001 charger, never unplugged it, often had batteries on it for extended periods (the TR001 is pretty good, too).
Early this year there were discussions about weird charging things (not TR001 or XTAR related), I dug up the Belkin timer as a contribution during the thread when someone asked about timers, decided to get one when I bought the XTAR. I actually picked up a second timer for the basement, all my power tool chargers are on a power strip driven from it.
It's all about personal comfort level. I do charge on a tray in the bedroom (convenience), I do use good chargers and batteries, but recognize things can break, I'm too lazy to futz with a charging bag (another good option for unattended charging -- I actually bought one but decided not to use it).