Persist aside, 10 min/level is a pretty long duration. By mid-levels, that means Heroics can last for a few hours. (Everyone should have a Lesser Metamagic Rod of Extend, after all.) In my experience, most parties don't spend longer than a few hours per day dungeon-crawling anyway. So Heroics is perfectly usable before battle actually starts.

Martial Study and Martial Stance are definitely the coolest uses for the spell. What maneuvers to pick up depends on what you already have. Every trip build would benefit from Mighty Throw or similar Setting Sun strikes. Casters can benefit a lot from Mind over Body or Action before Thought. Really, though, on non-ToB characters, the maneuvers you can pick up via Heroics are pretty similar to what you can get with a 3000-gp item.

Mostly, feats to gain with Heroics are just "whatever feat you want most, but haven't had a chance to take yet." There's not very many feats that are situationally awesome but not worth taking yourself. There may be a few, though.

Woodland Archer: time for some sniping.
Improved Disarm: oh, we're actually fighting humanoids with melee weapons today.
Improved Feint: we just met a monster with friggin high Dexterity.