Linguist can be quite fun, depending on the campaign. For the low, low cost of a feat which you otherwise wouldn't spend usefully anyhow, you learn three languages.
Seconded on this. The PCs in my campaign have already run into linguistic troubles more than once - can't read the writing in the dwarven ruins (they solved that one with a ritual), can't impersonate a goblin in the goblin-infested castle (yes, they have a way to look like one, but they can't say anything, which limits the usefulness), can't spy on the orcs in the advancing horde. I've been pretty generous about letting all the various creatures know Common, but that doesn't help when you're trying to understand what they're saying among themselves.
Do not underestimate the power of Linguist in a campaign that involves anything beyond combat.