Having switched to the Aquasana line of filters a few years ago, I cannot imagine going to any others. For apartment living, where the options of making changes or installing gear are more limited, the countertop AQ-4000 is an excellent solution for better water quality and the budget. When they figure out a way to keep the pressure buildup from making it so difficult to open and replace the "A" side filter, the system will be perfect.
Been using these filters for years with good results. One draw back we had is that the under-the-sink unit began to leak causing significant damage down stairs.
The filter system I originally purchased was extremely easy to install. I am on the "Water for Life" program and the replacement filters arrive promptly, every six months. Filters are a "no brainer" to change out...fast and simple.
Pros: Clean taste, Easy to install, Long lasting filter