It all depends on the cap and how much it costs if you exceed. If it affects the top 5% of bandwidth hogs, then all power to them. If it affects more, then I'll be more inclined to be irritated.
Wait and see before you get upset. Personally, my AT&T cable modem performs beyond my expectations and they would have to upset me a lot before I'd consider switching to the slower/more expensive DSL options that I have locally. The 128kb upload bandwidth cap barely affected me. Similarly, the 1.5Mb download cap is something that barely ever affects me. If they capped my downloads per month to 50GB, it wouldn't affect me at all. If they capped me at 10GB per month, I'd be more upset. But it also depends on the charge if you exceed it.
Still, wait and see the details.