LE: 250 MHz clock speeds
full retail: 275 MHz
difference in speed :275 - 250 / 250 x 100% = 10%
So theoretically if you are getting 50 fps now, you would get 55 fps with a full retail version.
If 5 fps bothers you that much, get the rage 3d tweaker and overclock it. If you are lucky, your card will still be stable at 275 MHz.
I have a full retail 275 MHz 128 MB card and love it.
Your control panel settings can affect your speed a lot as well. My card runs AH best at 1600x1200x32 with Anti-aliasing x2 and everything else cranked up all the way. I also disable video sync with no aparent penalties.
Catalyst 2.5 ran the fastest, 3.1 the slowest. Catalyst 3.2 seems to have recovered all of the speed of 2.5 and has fewer compatibility problems. I am hoping Catalyst 3.3 solves the only problem I still have with the 8500: Strike Fighters Project 1, which I can only get to run halfway decent by using the Rage 3D Tweaker to disable TCL (hardware terrain and lighting).
At $130 from Comp USA, the 275 MHz/128 MB Radeon 8500 was a real bargain compared to the $200 I paid for my Voodoo 5500. Though I must say the Voodoo 5500 still plays all my games very well with equal or better image quality and only 5% to 20% slower than the Radeon on average.