Just let me buy TF2 for $25. Shoot, I might even consider getting Portal for $25 too. Making me re-purchase stuff I have, and stuff that I don't want just seems like an annoying waste to me.
I do give my hats off to Steam, I check the weekend deals every weekend because they have some insane deals, awhile back they had a L4D for $25, and more recently I purchased FEAR2 for $25, and Crysis Warhead for $15!