I used workstation in a general sense.
iChat does not support MSN as far as I know }
You can load any non-Flash site just fine. You can also get by on many Flash sites. You can use AppleWorks, or "Office". You can load up older games. The 700 MHz iMac will have no problem playing back any 320x240 video thrown at it, but it will choke on the larger videos in the newer codecs. To play YouTube videos more smoothly just use the QTYouTube bookmarklet which magically converts the Flash YouTube video on any page into a QuickTime player.
iChat does not support MSN as far as I know }
It has FireWire 400 which allows you to connect hard drives or DVD burners. You can also get adapters if you want to replace the internal slim line with a DVD burner.