Any metronome will work, as long as you can quickly and easily adjust it. Volume control is nice (I assume you're using in-ear for this), but I don't think many of the fancy features are really necessary- subdivision, etc.
Also important is the ability to shut the metronome off when your band gets off from the click a little. There's nothing worse than when the drummer is fighting with the band.
What might work better for you (depending on you and your preference) is a tempo meter. Something like this would allow you to keep track of what tempo you're actually going, rather than give you an arbitrary click that you're slave to. The nice thing about it is that you can do accelerandos and ritardandos quickly, easily, and accurately.
my main problem is (recently I work with to many pop bands!) getting the tempo right for every song... once I count it off, I don't have problems keeping it. so as you said, I need something simple, with simple controls... just to get me started when I'm not confident about the tempo
I was also looking for things like Temp ref, cous I like to be a bit behind the beat, or to push it a little bit, but they are quite hard (expensive) to get in my country (maybe i should buy one when on tour abroad)...
I use the Dr. Beat DB-90 with the FS-6 foot pedal.
You can program up to 50 preset tempos into it and use the pedals to quickly toggle back and forth. I use a small mixer to feed the metronome and a monitor line into and use some in ear monitors to hear everything. I think this is the way to go (for me anyway).