By RCA I meant the connectors directly attached to TBC-100 board which are unexposed if you don't remove the metal cover. Anyway, I don't use the audio pass-thru either. Once when I measured my soundcards audio delay I checked how much effect the pass-thru had. Result was;
DelayAudio(-0.170) # Video TBC, Audio Direct
DelayAudio(-0.152) # Video TBC, Audio TBC
18 milliseconds delay compared to direct.

(so I guess they compensate for the video delay)
After quick eyeballing BM seems to be exactly what they were advertising. No problems with VHS etc when using TBC-1000. Quality clearly better than PDI (which already was very good). Capturing thru VirtualDub works fine (I can use ffdshow's codecs with it like Huffyuv). The final test is to see whether I can drag all my hardware and software to Windows 7 and finally get all 6GB of RAM in use.

I feel that AJA couldn't offer me much more personally. And AJA costs 2x as much if HD is a must. If you want some test etc with BM done just ask. This stuff needs it's own thread soon.