I have a Canadian iTunes account and live in the US. It works just fine for me. I can still buy apps and update them, on iOS and Mac. I haven't encountered any IP issues. The only downside is that I need to keep using my Canadian credit card, and there are some apps I can't download but could use, like Spotify.
Yes, tying the region of the account to the region of the credit card is a pretty damn flexible way to do it, given the movie and music companies are forcing them to tie their sales to regions.
Much better than the IP address BS you see from other companies.
