The Witcher is already significantly discounted, though. I'm not saying it won't happen, but $13 for it is really, really cheap and totally worth it.
That said, the only games I've bought so far have been games $10 and under (with the exception of Wallace & Gromit). I figure the games under $10 probably aren't going to drop any further, and if they do it probably won't be enough for me to get too grumpy. Save the bigger purchases until the end.
Also, I haven't actually mashed the button, but it looks like I can buy Steam games using my iPhone. Has anyone done this to confirm? I'm not going to have access to my PC until next week and I'll be damned if I'm going to miss more sales.