Not sure about my average stitching speed, but I know that lately I've been getting through about 800 stitches on my Treasure Hunt Bookshelf project in a weekend (which usually affords me at least 6 hours a day or so)
I totally agree with what BMH said!
Especially having something familiar on, whether it's a TV show, movie, book on CD, or music, is a huge help to me!
Also, I've noticed that I go faster if I have really good light, especially natural.
If I'm working with a lot of confetti stitches, parking my threads sometimes helps me feel like I'm going faster...big blocks of color do that, too (if I'm in the mood for that

)
And if all else fails and I can't see to pick up the speed on a project, I will often set it aside and work on something else for a while (couple of days...or weeks...or even months) and then when I come back to it, I seem to work faster (even if it's just in my mind)
And, above all, when I find myself getting on myself because I feel like I'm not working fast enough, I remind myself that there's no rush and to not stress about it...just enjoy the process!
Good luck!