I bought the AV a month ago, as soon as I knew when the os x player software was being released. I had heard great things about it, but was very skeptical whether or not it would really work. Setup is a snap, its own config software will open up ports on your router (i chose to do it manually).
Watching tv through the slingbox on an computer outside my lan was pretty simple. Instead of installing the software on each computer you will use it on (i'm at college so i don't always use the same computer in labs, etc.) I installed the program on my flash drive; it works pretty well that way, too. The quality is exactly what you expect; obviously it depends on your upload/download speeds. I'll put it this way: everything is watchable, and its not terribly blurry (although you can tell when the speed decreases). I'm able to control and watch my Tivo very easily, as it shows me the exat Tivo remote in the slingbox player. Obviously you can't play the video full screen (well, you can but it looks pretty bad) so that is one annoyance. If you have a hd set and plan on buying the pro and hooking it up to hd, think if that might be worth it (unless you need the pro for other reasons). Although I've never seen it, I don't think that hd contect would be what you would want it to be through the slingbox.
Generally I would say i'm not as impressed as other people sounded to be, but it is definitely easy to setup and use, and it does it's job pretty well.