+1, QFT. RCA digi-in is the single most important feature that the bulk of the recorders on the market are missing.
Other features:
Mic in with 9V PIP (enough current to power Church Audio mics or similar).
Line in with as low self-noise as R-09HR and M10
30 sec pre-recording just like the Iriver (IIUC some of the Tascams do have pre-recording, but not all models, and not as long)
Customizable GUI would be nice to have (Rockbox REP style) with rolling histogram, level bar scale, font size etc.
Less plasticky (not crucial though)
This said, I haven't owned any Tascams myself, just had them demoed for me at trade fairs.
Thanks a lot for doing the legwork, Chris - much appreciated. I'm positively surprised that Tascam bothered and figured out a way to tap the TSKB!