Wow, you've been around here for a long time.
Anyway, the best thing you can do is just go listen to one. They are a decent alternative in some rooms and make a great compromise to complex installs or limited space or wifey issues. They are going to be much much better than your built in TV speakers in most cases, but to compare to a true surround sound? Eh, thats really apples and oranges. Just go demo one or even better yet, bring one home and try it out and see if it fits your needs. But I'm sure you already knew everything I just typed.