I've seen them quite a few times and never bought one. Every single time, I peek over at the games available and see pretty much nothing that I'd play. I'd probably play Mario Kart, but not much more than that.
One thing is, it's not worthwhile for me to "invest" in another console when I get the majority of games on one. Most of my friends have an XBOX 360 (as well as quite a few family members) and I've purchased all of my games that come with extra peripherals for the 360 (Rock Band, Guitar Hero, DDR), so purchasing for a new system means I need to buy more stuff.
So, I'll stick with my 360 and my PS3.
Oh and there's one interesting thing that happened to me. I purchased my PS3 awhile back with the Chase Sony card and I posted on here once talking about all the issues I had using the card (even with a $0 balance and no payment listed for a month or two, it reported that my card was "past due"). Chase closed my account on me and deleted my 8,000 points (~$80). I'm still pretty pissed at them and called them up about it when I found out. I got the typical "We cannot do anything about it." spiel from Chase . I was going to buy a remote and another controller with that!