We had a TD Bank account when we moved to the US, so we just got a TD Waterhouse account. TD Waterhouse was an internet-only bank which was perfect for us. Plus I didn't need an SSN for it, which took over 3 months to get (long sordid story of US government incompetence). All the local banks needed an SSN. TD Waterhouse was happy with my Canadian SIN.
We were able to
transfer money back and forth between our US and Canadian banks with just a phone call and the bank's conversion fee (which you end up paying no matter how you transfer money). Transfers took place the next business day.
Fortunately when TD Bank became TD Canada Trust nothing changed.
However, this year TD Waterhouse became TD Banknorth and it's quite different (service is worse, to be honest). We got rid of our TD Canada Trust account before the change though, so I don't know if you can transfer money between TD Banknorth and TD Canada Trust. But it's worth looking into.
FYI we are probably going to switch from TD Banknorth to Netbank soon, since we have no reason to stay with them and their higher fees, and they are less internet oriented than TD Waterhouse was. (Fees are probably still lower than a full brick-and-mortar bank, though.)