From my own experience, I had just signed up for Dish just days before the Viacom channels were removed. In fact, my service was actually installed the day the channels were gone... but I wasn't worried. I knew it wouldn't last long, so I went through with it and stuck it out. Everyone was talking about it, but those that I talked to were on Dish's side.
Everyone I've talked to, or read from, who has switched from Dish to Direct have all mentioned Customer Service and Hardware Reliability/Functionality as the main reasons for switching. Some mentioned programming/value. None that I can remember mentioned Viacom.
Dish has far more serious issues than a few days of missing Viacom programming.
I switched and I do not regret doing so. I have found D* to be equal or superior in everyway except the super stations. TIVO is much better than the E* pvr's. Picture quality is equal. CS is eqal. Software seems to be superior. Multiple manufacturers is definitly a plus. NFL package is great. Pricing seems to be about the same. Just my 2 cents.