Yeah, we've had horrible experiences with Citrix, but these were all traced to the fact we didn't dedicate a big enough server for Citrix itself.
With your small volume of users though I think I would look into alternatives too. Citrix seems to have significant overhead for small numbers of users.
If you have decent bandwidth between the locations it might be cheaper to go with Win2K Terminal Services - since you'll probably be installing Win2K Advanced Server anyway. Citrix does have a reputation for better performance over lower-speed connections than MS's product alone though.
This sounds sort of like insane overkill for your situation, but I assume you a dealing with a moldy application that might be even more costly to modernize to use a thinner interface (i.e. web browser). I wouldn't be surprised to hear that the thing is DOS based - there just isn't enough $$ in these vertical markets for major upgrades to come quickly or cheaply.
It sounds like you're considering a SINGLE dialup connection from your laptop. Maybe the best answer would be some cheap or nearly free "remote control" software that dials into your office's desktop machine. Ask your computer guy about that - though he's probably looking forward to selling you that Citrix box!