It's a fun and useful archetype, like GolGolarion mentioned, but I personally wouldn't take it unless I'm playing a campaign where I know it'll come up a lot, and/or we're playing with Free Archetype. It's just not worth the class feat slots otherwise.
I've never looked too closely at the dedication, but now that I'm looking at the feats it provides, it looks great. I mostly play PFS, so I think I'm limited in the function by that, but even in PFS, I know of at least a few scenarios where this would have been really helpful to have. I may have to look at building a character utilizing it in the future.
I think that's a great character concept; and now I'm wondering if you would get a bonus to your DC if something tried to counterspell you and you were using different/multiple languages to cast spells. I think I'd certainly allow it as a GM if a player came to me with that idea.
I don't think you get a bonus RAW, but with spot translate even if you the only one that speaks the same language someone else can attempt demoralized.
Not with RAW, I would think that this would have to be GM discretion to get the bonus. It would be a cool way to reward a player that came up with an interesting concept.
It's pretty good value - 2 skill feats and an Expert bump in a useful recall knowledge skill is good as far as dedications go. It kind of has to be good value though, because the core functionality is easily replaced with consumable items.
It's also really easy to dip out of, having two archetype skill feats available - if you were going to grab the Multilingual feat mutliple times anyway, you may as well replace them with those, and get the bonus languages from the dedication.
Spot translate's funny - it helps your teammates who didn't learn a hundred different languages affect creatures with spells like Command. What did that guy say? Oh, they have a translator, apparently they meant "DROP PRONE," guess we gotta do that now.
It's certainly not a combat archetype, but it's not the worst way for characters to save money on scrolls of Comprehend Languages 3.
I think it's great if you travel to a lot of different places in the campaign, like Age of Ashes or Stolen Fate, or if your GM makes a point of using different languages. Otherwise it's so-so, there's probably a better archetype out there. But I really like it for RP in some of my characters.
I think the basic dedication is great, and useful. Unfortunately, it locks you in to picking two more Linguist feats if you ever wanted to take a different archetype, and I'm not really a fan of the rest of it.
I find feats like this, along with all of the creature type specific ones, are really campaign dependent. You either take them reactively once it becomes clear that it would be really handy to speak, say, Gnomish, or you need to metagame a little bit with your GM to know which languages won't be dud picks.
In my game, I would also find it totally reasonable to retrain a language that hasn't ever shown up, using less downime than it would normally require.