Feats that Grant SLAs - worth it?

[ShurikVch]

Feats that Grant SLA's (http://www.giantitp.com/forums/showthread.php?329656-Feats-that-Grant-SLA-s)
Feats that grant spells/spell like abilities (http://www.giantitp.com/forums/showthread.php?318492-Feats-that-grant-spells-spell-like-abilities)
Those threads are listing a number of feats which grant SLA or PLA, but are they worth it?
I mean - feats are one of the most limited resources in the game.
Dragonmarks are often prerequisite to something else, but besides it?..

(Because not all classes are equal, and "useful at 6th level" may be vastly different from "useful at 15th level", please clarify suggested build and level)

[ATHATH]

Well, they can qualify you for Paragnostic Apostle early, and Half-Fey and Phrenic are quite good if you have LA buy-off.

[nedz]

Some can be, most aren't.

Several feature in various build tricks - YMMV with these.

[MaxiDuRaritry]

Some can be, most aren't.

Several feature in various build tricks - YMMV with these.This.

Unless you're abusing the rules, it's almost never worth it to bother with taking a feat for SLAs. Most of them are cantrips or weak 1st level spells (mostly cantrips), and spending a very rare and valuable resource in exchange is basically setting your feats on fire.

Now, if you DO abuse the rules, or you use the feat as a prereq for something quite powerful (such as taking a dragonmark to qualify for Mark of the Dauntless), it can be worth it. The immunities granted by MotD are totally worth two feats, especially when you're a wilder and want to shed the biggest millstone around your neck.

[tiercel]

Fey Presence (Complete Mage) is actually pretty nice for minor minionmancy-inna-box (thanks to charm monster and its long duration, neglecting the lesser benefits). Downside: eats two feats, have to be 6th level, and of course the opportunity cost of what you could have had instead.

If you're nonlawful, without significant casting of your own, could use a (situational) Will save buff, have a non-awful Charisma, and have two feats to spare... (and frankly, if you're in this deep, you might consider other Fey Heritage line feats)

That's a lot of ifs for what's arguably one of the best SLA feats, which says a lot about most of the others (barring shenanigans, as has been pointed out).

[ATHATH]

Are there any PrC's that Fiendish Heritage's Summon Monster SLA can qualify you for?

[Troacctid]

You mean Fiendish Legacy? Sure. Paragnostic Apostle and Wayfarer Guide, off the top of my head.