We have had two
The first one we bought from Costco several years ago - a Watts WP-4V. It worked well, but the 'faucet' started leaking. When you closed the handle, it started going too far back and you would have to move it slightly forward again to keep it from dripping.
I looked into replacing the faucet and a complete set of filters, including the membrane, and it appeared to be a better decision to just buy a new system
Started researching on Amazon and ended up buying their best seller/highly rated system by Apec. their Essence ROES-50 system. We have had this system for just over a year and so far so good. I did find out that if you wrote an Amazon Review they would give you a free filter set (3 filters) which in my mind partially explains the high number of reviews
The big difference between the two is the Watts system used an 'air gap' faucet. In an non air-gap faucet, the drain line from the membrane is plumbed into the sink drain. If the sink drain line gets plugged up, water can flow back into the RO system and contaminate the membrane although they do have a check valve. In an air-gap system, the drain line from the membrane runs up to the faucet and if for some reason the sink drain line gets clogged up - the faucett will start leaking out the discharge water which you can see and realize that something is wrong
Some areas require an air-gap by code, some don't. Personally, I think the air gap system is better but I do not have the drain line plumbed into the sink drain - I run it out the back of the house (check valve in the line) and we catch the water in a 5 gallon bucket to hand-water the plants. RO systems waste a lot of water