I would definitely get one. Once you've got one, you won't ever want to be without it.
Some of the companies that advertise in the Sunday papers have high margins and high-pressure salesmen. Chnaces are there will be a local water-softener company in your area that assembles, sells, installs and repairs them, and also delivers sacks of salt.
Ring round a few and say "do you repair water softeners? What's your charge?" as you want to be in with a company that can repair if necessary. If you buy mail-order or from B&Q you will probably have to throw it away if it goes wrong, but the parts are readily available and the machine is far simpler than a dishwasher.
I think mine went about ten years between faults. The first time my local company repaired it, the second time I swapped it for a reconditioned one.
Have it installed by the incoming water main. It needs to be plumbed to a drain for the rinse water during regeneration. It must be easily accesible, away from frost, and preferably not upstairs or behind anything as you will need to put blocks or sacks of salt in it. I have the 25kg sacks delivered by the local company, they are pretty heavy. 10kg bags work out more expensive, so do blocks. The salt dust is very corrosive so try not to get it anywhere near your own car.