MARK_NOTARUS and Sean T. Fucking O'Connor pointed me at the now-fully-functional cygwin native (read: doesn't require an X server) rxvt. Two minor obstacles and I'm up and running. One: You have to install the Bitstream Vera font set into Control Panels/Fonts. If you don't, you get windows where each character is double-spaced horizontally. You can turn off the font and boldFont resources in /etc/X11/app-defaults/Rxvt, but then you get a small font that's kind of hard to read at a comfortable seating distance. Two, you have to stop using pscp and use the now-functional cygwin scp. pscp, when NOT built against cygwin (in other words, its binary distribution) doesn't grok cygwin's tty mechanism, so it doesn't know how to handle non-echoed passwords properly. (It echos your password (!!) and then doesn't pass it on correctly, so the connect fails.)
So here's my app-defaults file:
Rxvt*background: black Rxvt*foreground: green Rxvt*cursorColor: red Rxvt*scrollBar: true Rxvt*scrollBar_right: true Rxvt*font: -bitstream-bitstream vera sans mono-medium-r-normal--*-160-*-*-m-*-iso8859-1 Rxvt*boldfont: -bitstream-bitstream vera sans mono-bold-r-normal--*-160-*-*-m-*-iso8859-1 Rxvt*saveLines: 2000 Rxvt*loginshell: true Rxvt.backspacekey: ^H
The shortcut in the Quick Launch bar uses the target
C:\cygwin\bin\rxvt.exe -title rxvt -e tcsh -l
Also, rxvt properly groks the xterm title bar control character sequence. Finally, I get my usual title bar back (pwd user@host). It's been a bitch without that, having eight or ten windows stacked in the task bar with no way to tell which 'tcsh' window is the one I want.
[Edit 4/13/09] Per jessebunbun, there's a screen shot in the comments. Also, Bitstream Vera has a lower-case 'l' that is very distinct from the digit '1'. That's a HUGE win there.