I would try before you buy, same with the other guys as well, use a Galaxy and a win7 phone. Also it wont be long before the super sweet looking nokia 800 lumia comes out. worth a look before you throw your life away with an apple.
its faster than the older models and it seems like the antenna issues have gone away, but its still an iphone. if you are okay with apple telling you what you can and cannot do with a phone you own then go for it.
if you want a smartphone and want control, go with a dualcore android phone. it might not be as polished as ios.. and the appstore might not be as great..but you have control to do pretty much whatever you want.
windows 7 phone... i havent heard much activity in that sector. at this point in time i would find it hard to recommend as it just doesnt have enough going for it to warrant checking out.
if you've ever owned an apple product (i have an ipod) then you would realize the deathgrip they have on usage. for instance i can copy songs to my ipod, but i cannot transfer them back onto the same pc even if they were bought using the itunes store. dumb right? welcome to apple.
i don't have any direct experience with the iphone (never had, never will) i can not give specifics but it appears that this is tied to itunes for syncing as well. as for the app store apple has a tight leash on devs...which has a good side but a bad side as well.
with android devices you can easily do things such as ...
changing themes, colors, launcherbars without rooting
free tethering to your laptop with root
play flash video
drag and drop music, video, etc to your phone
as for windows phones go, i wouldnt suggest one as they dont have enough market share to be competitive.
as i remember nokia phones used to be pretty good in the past however i read a few articles on how they were going through some problems which has lowered their market share. as such its hard to say that just because one manufacturer supports wp7 that it will instantly take a large market share.
i'm not knocking the hardware or included software of wp7. all i am saying is that there are at least 10x the resources available for ios and android. these include tech support forums, applications, etcetera. also remember that i said that i wouldnt suggest one (this is an opinion). i'm not lying there, i think wp7 needs to bring something new to the table in order to be a good choice.
in any case it is up to the OP to decide what they want.