My favorite improvement that our agency made to our workspace isn't the dual monitors, isn't the shorter hardware upgrade cycle; my favorite improvement is the sit-stand desk. Seriously. I think every desk worker should get something like this.

I used to have all sorts of minor aches and pains from sitting most of the day. Now I spent an hour standing, an hour sitting, plus the usual breaks, etc. I'm more productive and happier. If your company won't buy one for you, buy it yourself. It's worth it.