I probably order room service one out of perhaps every 100 nights or so, and generally because I am starving, its late at night and there are absolutely no other options available. I generally avoid it because:

1) The selections after 9, 10 or 11PM are generally terrible.
2) Even when the selections are decent, the food is generally not that great.
3) As has been said numerous times above, the prices and gratuities, etc. are often ridiculous, especially for what you get (someone wrote about $12 for an entree.....that is cheap, my problem is when a "top" hotel in Europe wants $40 for a soggy club sandwich and that is the only option.
4) Based on the time of night that I need it I often find that the potential wait times are ridiculous.

I do notice when I travel with my assistants and the like they will order room service a ridiculous amout, I suppose its novelty, or that the company is paying or whatever, but I tend to find that serious road warriors tend to either follow my pattern, or oddly enough will order breakfast most days, as I do not eat breakfast, I do not really get that.