So, everyone rushes to boot off, en masse, the feats that give a combined +4 to skills, but you think a mere +3 is going to stay to the very end? Curious!
I forgot that it gave +3, because IMC it gives +4, but regardless, it's still a great way to spend a feat slot. You can use it to get impressive results on skills you specialize in (Bards with 30+ Perform rolls! Rogues with 30+ Sneak rolls!), and you can also use it to shore up something you're typically not too impressive with (that ugly fighter who wants to try to fient suddenly stands a chance he didn't before), or that circumstances make difficult ("that heavily clad knight sure can tumble better than I would've expected!") It's a great way to add some dimension to the character, and is quite useful once you figure out which rolls are going to be made most often in the campaign (such as Detect rolls to see and hear things approaching, or whatever). +3 is a *big* bonus, and if your characters are making a lot of skill checks (of any kind) it's really useful to have.
Sure, Power Attack is nice, but not everyone can use it. When was the last time you saw a Wizard with Power Attack? Weapon focus is more useful! But from Wizard to Barbarian to Rogue to Cleric, all can benefit from Skill Focus, and can benefit greatly from it.
If the +2/+2 feats applied to ANY two selected skills, or the +2 to Save feats applied to ANY selected save, I'd give them about the same running.
In my mind, Skill Focus is the single most useful feat out there. Others have their uses, but they are either pretty niche (e.g.: only a certain character type can benefit from it). Everyone loves a +3 bonus, though.