Nope .....
Vista TCP/IP Management - Don't Use TCPOptimizer:
"Well ... here's a shock ... something Vista does well ... in fact very well:
I heard Vista dynamically manages settings such as the TCP receive window that you can use TCPOptimizer and other programs to set to improve internet surfing performance.
If you use TCPOptimizer on a Vista machine guess what? It slows your internet connection down."
On XP and Win2K it is very unusual not to see a speed increase. It doesn't work too well on all wifi receivers though. Some just stop working.