I've heard from people who've been waiting two years or even more to hear back from Tor. IMO, it's simply not worth submitting to any of the SF/fantasy imprints without an agent, even those like Tor that will look at unagented manuscripts. The timeframes involved are just too long--and when your ms. is looked at, it is unlikely to get the kind of careful editorial consideration it would if it came from a good agent. It'll probably be an intern or an assistant glancing through the first few pages, or a slush party where a bunch of editors sit down and say "OK, guys. We have 500 submissions and five hours. Let's get through them all!"
Things do get bought through publishers' slush piles. Editors love to talk about their slush pile purchases, because it make them feel good. And that's great. But most books that sell to Tor and others sell through agents.
- Victoria