I have one of these from a wireless keyboard/mouse combo and it is a good size and has performed very well. I have had a problem with the 'back' button recently where it has taken 2 presses to get it to go back though.
I'll probably contact Logitech support and let them know. They've been great in the past. 2 1/2 years into the 3 year warranty on my previous keyboard/mouse combo it gave up the ghost. Within 2 days I had a new combo that was a step up from the previous combo since it was no longer available.