Is Illusion Adept worth it if you're already an illusionist?

Illusionist already gives you verbal-free illusion spellcasting at level 3.  You're also already adding illusion spells to your spellbook for free.

So is Illusion Adept worth the feat slot (5 prepared spells you were probably going to take anyway, cast with no components)? 

(It's kind of a feel bad moment that you're sort of doubling up on abilities, and a non-illusionist with the feat can do some of your key subclass features, but better.)

Alternative thought is spell subterfuge.

I suppose it depends how much you need the feeling of absolute gain from your feats. Even if you already have the spells in your book, it's still 2-5 freed prep slots for additional spells, and lets you take more niche picks for your other extra Illusion spells. Removing the other components and making the Investigation checks more difficult depends on the kind of campaign you're in.

Regarding Spell Subterfuge, note that you only get to use the meat of it 2-5 times per LR and it doesn't actually do anything to conceal the casting itself. It's good for letting your squishy caster move away from enemies a couple times, but less useful for the "I try to fool a crowd without doing crazy hand gestures and/or waving a wand/staff/crystal around".

Quote from The_Ace_of_Rogues >>

I suppose it depends how much you need the feeling of absolute gain from your feats. Even if you already have the spells in your book, it's still 2-5 freed prep slots for additional spells, and lets you take more niche picks for your other extra Illusion spells. Removing the other components and making the Investigation checks more difficult depends on the kind of campaign you're in.

Regarding Spell Subterfuge, note that you only get to use the meat of it 2-5 times per LR and it doesn't actually do anything to conceal the casting itself. It's good for letting your squishy caster move away from enemies a couple times, but less useful for the "I try to fool a crowd without doing crazy hand gestures and/or waving a wand/staff/crystal around".

 If you're hidden, casting any spell doesn't end hidden on you so long as you can end in appropriate cover (which presumably conceals the casting itself, since you remain hidden).  And that part has no limit per day.

Sure, but the viability of that has already been discussed to death elsewhere, so I’d rather not reiterate all those points. And that seems rather less viable for out of combat utility, imo.

Quote from The_Ace_of_Rogues >>

Sure, but the viability of that has already been discussed to death elsewhere, so I’d rather not reiterate all those points. And that seems rather less viable for out of combat utility, imo.

 Well, in this case you can assume Hidden actually happens, because I have yet to play at a table that didn't run the Hide Action straight RAW, no DM interpretation.

Definitely worth it.  Disadvantage on the intelligence check means no one will discover your illusions.  Hidden isn't required, mobs won't shoot at you at disadvanrage, and won't hit you if they do.