The only formula that my son would willingly eat was premixed liquid enfamil lipil with dha etc (we tried most of them, btw).
2 things:
1) I tasted ALL of them, where my son couldn't see me, nearly every time I warmed them up. Most of them were terrible, AND all the ones that had "gentle proteins" (aka, already partially broken down, aka partly digested) went bad inside of 20 minutes. My friends who use these types have to mix and serve them cold. They're wretched in a blink (20 min) if made warm... they start to turn almost immediately, are sour within 10 minutes, and are worse than spoiled rotten in 20-30. Ugh.
2) The premixed ones have kind of an oily, silken feel to them, but they're ungodly expensive. Many babies won't take the powdered kind at all in the beginning if they've been lucky enough to get the real thing first. So it's definitely a good rule to try the liquid if you're having formula refusal. FORTUNATELY most formulas have sample cans, so you aren't out $20 per can just for taste testing. :)