Depending on my mood I use screen, cu or minicom. screen can tie in with the lrzsz tools to do uploads/downloads. However mostly I don't care about flow control (or rather, explicitly don't want it). In my experience minicom is the best tool when using flow control, because it makes it very clear what it's doing. Otherwise I tend to use screen these days (which apparently can handle flow control, but it's a while since I've needed to).
Le Putty appears to be PuTTY with zmodem support, but I've no experience of it: http://leputty.sourceforge.net/
J.
Hmm ... the use-case is connecting to/from an 8-bit micro, so I'm looking for something that isn't using a protocol like zmodem or kermit - just raw transfers. It looks like C-Kermit can be made to do this, and I think minicom too. I'm not sure the others you've listed will fit the bill, unfortunately, though I'll have another look when I actually have the setup to play around with.
It's a shame that it looks like there's no easy GUI-type tool (like Tera Term 4 on Windows) which might be easier for newbie users, but as long as something works, one can't really complain. :)
Cheers for the suggestions,
Peter.