I have two issues with browserstack: first, latency. It’s not always bad, but it’s always noticeable. It’s a pain in the butt to do something and then have to wait 100ms to see if it did what you expect —or worse, a whole second, just to be sure that it didn’t work.
Second, and this isn’t really a big deal, I signed up when it first came out, and the deal was you’d get 30 minutes/ month free as long as you kept the account. Well, that didn’t happen. Maybe it’s a fluke… I honestly am not concerned enough about it, nor did I end up using the service enough, to press the issue. But it nags at me.
Don’t get me wrong, though. All in all, it’s a great thing, and I still recommend it to people. But when it comes to IE testing, the VMs rock.