We bought one of these two years ago and it's been great....

https://www.amazon.com/gp/product/B005LKKMYS

This replaced an old Kenmore RO system from Sears that was installed in 2003. The iSpring unit has a mineral cartridge to add back in some of the stuff plain RO systems strip out and that's been a plus. You could definitely taste the difference and even feel the difference in your mouth. I guess it's supposed to be better for you to have those minerals in the water.

We live in an area with really poor water pressure (40 psi on a good day) which makes the RO system less efficient and take longer to refill the tank. If you have decent pressure the same system without the pump is much cheaper....

https://www.amazon.com/iSpring-RCC7AK-Capacity-Drinking-Remineralization/dp/B005LJ8EXU

Since we already had an RO system I didn't have to drill a hole in the sink for the faucet. The rest of the install is pretty easy for anyone with a few common hand tools and who can watch and learn from a YouTube video or two.