I use Remote Acces (first with NT4, now with 2KServer) with little trouble. Our risks are limited due to the size of our firm (small). It's Remote Access, not VPN, so without the number, a user name and password for an account with RAS permission, access isn't possible.
The only problem I've had is the dial-up part. The limited connection speed can be a pain when trying to transfer drawings. I use the connection from home mainly to work on admin type things such as programming, intranet modifications, etc. When I need to work on drawings, I zip them first at the office, then transfer the zip across the RAS connection.
I'm not sure exactly what you're trying to accomplish, but if you want your users to have access to your data from outside the office, I would think that a VPN would be your best bet. From what I understand, a reasonably priced firewall would serve most of your security needs (along with general network security issues on your server, of course).
In the above scenario, I don't know of any advantage to using FTP. It would seem to me to be just one more thing to keep running/functional as well as the issue of moving files back and forth to the FTP location on your server. (Not to mention FTP apparently adds it's own security concerns, as if a connected network doesn't have enough, already.)
CAUTION: I'm not a certified anything, so by all means, use caution when digesting my drivel. And if anyone disputes anything I've said, don't be shy. The issue is too important to leave misinformation unchallenged. ;)
HTH