I got an i9000 Galaxy S
+ Best hardware
+ Best screen
+ DivX/Xvid/mkv(h264)fullHD playback out of the box
+ Music player much better then stock Android
+ Easiest Android phone to get root and/or install custom ROM, no need for goldcards etc, easy to unbrick a phone.
- Samsung KIES(no OTA updates, KIES is windows only)
- Samsung TouchWiz(I use LauncherPro Plus)
- Lag, lag, lag, because of Samsungs RFS filesystem(see XDA)
- GPS sucks, SGS always shows me a few kilometers off, my HTC Tattoo shows me where I am, both in Google Maps.(there are a few fixes but no good one)
+ XDA-Developers, you can get lag-fixes or get a custom ROM, as Darkys or Insanity ROM seems to be the best right now when I write this, ie, no lag

XDA makes the stuff Samsung should have done
For me the only minus is the GPS, when I use the night sky app to check stars, everything is wrong.
All other errors can be fixed through XDA
It's the best phone available (perhaps except Nexus S, but it got no SD slot) right now.
If I were you though.. .I might wait to see what's coming the first few months 2011, dual core phones, gingerbread etc...
edit//
forgot a minus

- Waiting for Samsung to update, and when they do, waiting for them to fix the update.. (Scandinavian froyo jpa to jp6 etc.. )
// endedit