Hi Keith,
I've recently been using TBW with the 6100 to make sepia prints. TBW has a really nice sepia curve that is beautiful on matte papers (and a nice, matte WR satin cloth that I profiled and really love for gallery wraps). I haven't been able so far to replicate this sepia with CS/LR toning and custom icc profiles using the Canon driver. The nits I have with TBW are that its is a bit buggy (I keep running into new ones now and then) and I agree with your evaluation of the paper sizes issue. My 6100 always generates GARO W1234 error messages when printing to 24 inch rolls which is just another minor, but irritating issue. I must turn off Airport on my Mac when the printer is on with an ethernet connection or it won't print. You get the picture - needs more fine tuning but otherwise very nice for some types of prints (sepia in my case).