I'm kind of in the same boat. I have a bunch of PW II's. What I'm thinking of doing is getting a Mini
TT1 and a Flex TT5. I'd use the Mini on my camera in the studio to trigger my old PW II's and on location when I take the Flex TT5 to trigger my 580EX with the benefit of TTL. Having TTL on location seems like it should save time, allow more flexibility in positioning the light and the camera, relative to the subject without having to re-meter all the time, and also use high-speed synch to shoot with a shallow DOF if that suits me. I've hesitated because of the cost and RF issue.
Cameras: 1DX, 1D4, 20D, 10D, S90, G2
Lenses: Canon 10-22mm, 16-35mm f2.8L II, 24-70mm f2.8L, 70-200mm f2.8L IS, 300mm f2.8L IS, 200mm f2L IS, 50mm f1.4, 50mm f1.2L, 85mm f1.2L, 1.4x TC, 2x TC, 500D macro, Zeiss 21mm
Lighting: 580EX, Elinchrom 600 RX's, D-Lite 4's, ABR800, 74" Eli Octa, 100cm/70cm DOs, Photoflex Medium Octa and reflectors, PW's, Lastolite Hilite, Newton Di400CR bracket