Swarley:
Can't change install path
Frequent mandatory updates of the client that not only take upwards of 5 minutes to complete, but they never tell you what they do.
Auto-updating, which frankly pisses some players off.
Additional hard drive memory and CPU footprint.
I'm not entirely sure why you would like a different install path, tbh.
Frequent updates? Again tbh, if you're referring to the Steam client itself, doesn't appear to be that frequent.
Auto-updating, I can see being a problem for users with slower than ideal internet connections. But I'm certain this can be disabled, and Steam can be offline.
Memory and CPU footprint shouldn't be too big a problem for most users. Todays games still do not take full advantage of memory and CPU power on recent PC's. But some users want to leave as much resource available for the game. Any noticeable difference should be very minimal.