I've had one for 5 years. Really, really like it, and still use it a lot.
A few points:
1) Put it as close to an entrance as possible. The further away it is, the less you will use it over time. Plus, if you live in an area that gets snow, you will have to dig a path to it/etc.
2) It is very, very easy to maintain. Add chems once a week, drain/fill three to four times a year. That's it.
3) It is amazing in cold weather. Not so much in hot weather, though. We haven't been in ours since early June. I keep it running, though, as it's easier to do that than shut it down / restart. Plus, if my back hurts, I want to be able to use it. From Oct-April, we use it 2-3 times a week.
4) Make sure your deck can handle the weight.
5) Depending on your electricity cost, it could be anywhere between $25 and $50 a month to run. (actually, $50 is probably high - I live in one of the more expensive areas, and I estimate it costs about a dollar a day).
Enjoy! Having a hot tub / spa is really a pleasure.