Keep in mind that TS and Vent aren't going anywhere, and as I said in my Voice Chat hands on, it's very likely that a lot of guilds (especially bigger guilds), will keep using those. But my guess is also that a lot of people will use both-- TS in raids, and the builtin voice chat in PuGs or more private groups. So if you're planning to use voice chat at all (even if it's in conjunction with a third party voice program), mark yes below.
And if you don't think you'll ever touch it, either because you're sticking to third party, or you don't want to voice chat, mark no. Who knows-- maybe Blizzard's overestimating demand for the feature in the first place.