The 3 stage filtration unit was very easy to install and came with clear and concise instructions. The only item I had to purchase was a 1/4 to 3/8 press fitting adapter as I already had a faucet mounted and it was 3/8 and the outlet tubing of the filtration unit is 1/4. However, 1/4 is a better outlet size as it reduces the flow rate to what I believe is the correct rate of water flow. The water taste is excellent. You need to be prepared to run the water for few minutes after installing filters to flush them out. I purchased my unit with the lifetime filter replacement program, however, being a single man I am not sure if I will use enough to justify replacing the filters every 6 months. Luckily you are not tied to a contract with the filter replacement program and can stop it at any time and buy then yourself whenever you may need them. In a couple years when I do some re-configuring of my incoming water routing and replace the standard water heater with an instant one, it will free up room in the bottom of the "closet" where the water heater is and I will be purchasing a whole house filtration system from Aquasana. In my search of water filtration units, I could not find any better value in the product I purchased and have fully enjoyed it thus far. I highly recommend Aquasana and their products.
I have to admit, after reading some of the posts I was a little worried about installing the unit. It was a lot easier to install than some people suggested. It took me about an hour only because I had to run to the local hardware store to pick up a long socket wrench. As for quality: I've had the units for about a month and the quality of the parts are impressive and the water coming out of the unit tastes really good.
We have had our Aquasana system for only a sort while so can't attest to longevity of system or filters but what I find remarkable is how smooth the water tastes and I tend to drink much more! I use it for coffee so that tastes better as well.