As I read the OPs post, there is only 1 data line to this remote site. If so, then the answer to my question below is most likely negative...
In my (limited) experience, it is not a matter of performance, it is a matter of uptime.
How much work could those remote users get done if the T1 is down, and what is the expected and worst-case reliability of that T1? Could a remote DC provide authentication and DHCP/DNS for the users so that a 'meaningfully large' set of applications would continue to be available, even if the T1 is down?
If the site is dead in the water as soon as the T1 is down, i.e. the remote users can't really get any meaningful work done without that data link, then a remote DC makes no sense IMHO. The same goes if the site has lots of meaningful work to do, but that work doesn't require any IT systems. But if the DC could enable the use of other IT systems, then it is valuable.
If you set up a remote DC, then think about Windows 2008's Read-Only Domain controllers, and consider moving other services closer to the users for performance.