I've got an Intex one, but I imagine will be similar to the lay-z spa range.
We love ours, but as MikeB mentioned it still requires the same amount of effort that goes in to a proper hot tub. You'll need to check the water on a regular basis and adjust the chemicals accordingly. If you do this then the water should last a decent amount of time (depends on how much you use and how many people you squeeze in to it

) So long as you're willing to put in a the effort for maintaining it I'd say it's definitely worth it.
You can't use it when the temperature falls below 4, or you risk damaging the pumps, so definitely not all year round.
Again another thing to remember is the running cost. It really needs to be left on all the time to keep the temperature up. Ours clicks on when the temp drops below what we set, then switches to filter mode once it reaches the correct temp. The cost seems to run about £10 a week (but depends on your usage, supplier and tariff)
I can see the image might be a problem with the cheaper models, but the newer, more expensive ones seem to mimic a proper hot tub now, definitely don't feel the one I have being overly chavvy. It's a good alternative if you don't want to fork out several thousand for a proper one or a stop gap to getting a proper tub.