I plan to retire the TiVo HD as soon as its yearly subscription runs out in January, provided that I am happy w/ the Roamio. Don't know if they'll add more SDV channels esp. since they are going all digital and dropping the bandwidth-hogging analog feeds. Nonetheless, I'd rather have a working TA. You'd also think that the continued installation of fiber would gradually mitigate the need for SDV. I don't think such a device is used w/ FiOS when you have a TiVo.
The Charter tech support person (wish I had a name/number for my future needs!) called back this morning and he was able finally to get the 2nd TA working. 3.5 hours of working w/ CSRs and a trip to the Charter office to exchange what was most likely not a bad TA. But it's all working for the moment and, based on my experience w/ the TiVo HD setup, it will be reliable from here on out.