A lot of fender factory strat pickups sound just fine as is. Plenty of guys are using whatever came in the guitar. Probably the strat bridge is the most upgraded pickup . . . usually they're a little lighter than people want and there are plenty of cheap hotter options to try out.
As far as the sound of strat pickups, they're pretty awesome. If you play clean or with just a tiny amount of gain they're much more pleasing sounding to the ear. They seem to pick up fewer harmonics, so you get a purer sound. Typically they don't compress as much as humbuckers so feel a lot more dynamic . . . which can be good and bad. But all that awesomeness comes with a downside - the hum. There are noiseless single coils and some of them are pretty good (probably couldn't hear a difference with a band playing), but every time I do a blind sound test between SSL-2s and one of the noiseless options on their own I prefer the SSL-2s.
FWIW - Flat pole strat pickups make me happier too, as the staggered ones never give good string to string balance for me. The G string is always way too loud and the high E never seems quite loud enough.