And I'd note that, unlike HIV, which was mostly younger patients, the HCV patient population is likely to be older (in the developed world) and thus a large fraction of the HCV population will be on some of these other drugs.
RE:ABT
The tolerability of the four drug combo is quite favorable compared to existing SOC. Ritonavir has been used for much longer durations than 12-weeks in HIV therapy so this should offset concern of use in older populations IMO.
You point to the potential shortcomings of using ritonavir. I myself have looked at ABT-450 (and ABT's combo) as somewhat flawed considering the apparent need for boosting. Yet are we sure the activity of ritonavir isn't what helped lead to such high SVR rates in the overall combo?