I had an Endless Pools Fastlane installed when I built my pool six years ago. The Fastlane cost me CA $10,350 + tax and installation was CA $700, although that's just to put the unit together and mount it in the pool. The pool builder ran all the electrical, conduit, and hydraulic hoses, so I'm sure the installation would be way more had all that not been done already.
We've used it quite a bit although mostly for the kids. It's strong enough to make an 8 shape current that pushes you and sucks you back indefinitely. For swimming, the only challenge I found compared to a regular pool is that you can't drift out of the current. But, as someone pointed out, I feel that forces you to be even more aware of your form. I don't really understand the "pushing" feeling people mention. Maybe if you're trying to swim leasurely, your hand feel like they're pushed by the current, but if you're really trying to get an exercise you're "pulling" on the water so much harder than the machine pushes it that you don't really feel it.
Finally, to the maintenance; I have a salt water pool and the installer said it's perfectly fine in a salt water pool. They also said I don't need to take it out in the winter. I should have read the instructions because none of that is true. This year the Swim Unit started leaking oil into the pool and getting oil out of a pool is not easy. The problem turned out to be a rusted fitting on the motor that sits in the water. Replacing the motor and oil is $1,500, which you're supposed to do every 4 - 5 years. Also, the hydraulic hoses that sit in the water have to be replaced every 2 years if installed in a salt water pool. So the maintenance costs are quite high. But with proper winterization and care, I think it can last a few more years than it did for me and $1500 - $2000 every 7 years or so to be able to swim in your own pool is worth it in my opinion.
P.S. one huge advantage with the Fastlane is that you don't have to put in a pool that takes up your entire back yard. Unless you are fortunate to have a back yard where you can fit an olympic size swimming pool, no other back yard pool is big enough for swimming. You don't even need to come up for air in a 50' pool, which is quite big. Anyway, my pool is only 12' x 24' and only takes up 1/3 of my back yard and it's still better to swim in than any other backyard pool I've ever been in. Not to mention that a small pool will save you a lot on chemicals and heating.
We've used it quite a bit although mostly for the kids. It's strong enough to make an 8 shape current that pushes you and sucks you back indefinitely. For swimming, the only challenge I found compared to a regular pool is that you can't drift out of the current. But, as someone pointed out, I feel that forces you to be even more aware of your form. I don't really understand the "pushing" feeling people mention. Maybe if you're trying to swim leasurely, your hand feel like they're pushed by the current, but if you're really trying to get an exercise you're "pulling" on the water so much harder than the machine pushes it that you don't really feel it.
Finally, to the maintenance; I have a salt water pool and the installer said it's perfectly fine in a salt water pool. They also said I don't need to take it out in the winter. I should have read the instructions because none of that is true. This year the Swim Unit started leaking oil into the pool and getting oil out of a pool is not easy. The problem turned out to be a rusted fitting on the motor that sits in the water. Replacing the motor and oil is $1,500, which you're supposed to do every 4 - 5 years. Also, the hydraulic hoses that sit in the water have to be replaced every 2 years if installed in a salt water pool. So the maintenance costs are quite high. But with proper winterization and care, I think it can last a few more years than it did for me and $1500 - $2000 every 7 years or so to be able to swim in your own pool is worth it in my opinion.
P.S. one huge advantage with the Fastlane is that you don't have to put in a pool that takes up your entire back yard. Unless you are fortunate to have a back yard where you can fit an olympic size swimming pool, no other back yard pool is big enough for swimming. You don't even need to come up for air in a 50' pool, which is quite big. Anyway, my pool is only 12' x 24' and only takes up 1/3 of my back yard and it's still better to swim in than any other backyard pool I've ever been in. Not to mention that a small pool will save you a lot on chemicals and heating.