We needed a casement/sliding AC because of our older ranch windows. We had to bite the bullet on the high price of the tall units because that is all that would fit...but we definitely don't really understand why these are so expensive compared to your average AC unit. The installation process was long, and was not the easiest either. Had to be creative and improvise at times and the instructions are not really as thorough as you would hope. 

The unit works well...we needed it to cool the master BR and it does great, and also helps cool the other 2 BR area on the upper level of our split level ranch. With a fan in the hall blowing downstairs toward the main level we also get some cooling benefit on the main level as well. Definitely does it's job. Also, the filter is super easy to clean with a dustbuster.