I've got Bilstein 5100s on my Tundra, installed last fall. Difficult to say how much of an improvement they are over stock, as the Tundra had 250k on the originals, and the originals were Bilstein 4600s. There was definitely an improvement in ride quality/control, but again the truck had 250k when they were changed. The truck is very controlled over rough rail crossings, no issue there. It was getting a bit bouncy. The 5100s do have a good reputation as a fairly inexpensive upgrade from stock.
The nice thing about the 5100's is that there's three different settings for lift for the front shocks (0, 1.75, 2.5" I believe but you'll have to look), so you can level it a bit if you choose. Price was $1600 installed all around, including tax. If you have any other questions let me know.