I have the 6.6 fluval chi. My betta loves it. The flow is barely noticeable. I live in the humid tropics, so I've only had to top off once per week so far. We'll see what winter brings.
I added a couple of mystery snails this week and was scared they might escape, as they are known to do. So I went to a craft store and got a thin but not flexible sheet of plexiglass (cheaper than their cover). I cut a cover out for the top of the chi (a challenging task, but using a professional plexi groove tool made it alot easier) and it works great... keeps in the moisture and prevents jumps and break outs. Totally unobtrusive. I'm hoping this means that I won't have to top off at all and can just do once weekly water changes.
I have a bunch of plastic plants in there, but honestly the footprint is so small (10x10 inches) that I think I spent less than $25 between 3 kinds of plants, standing bamboo, and the gravel.
If you like the tank's looks, as I did, you will love it once it's set up -- you can gradually add decoration. If you find the filter is too strong for your betta, you can add a square of cheesecloth inside the filter compartment (cut to the same size as the filter material and it will slow down the pull.