I dont own one, but they look like decent filters. Although, they are pretty expensive for a HOB filter, and I dont think rena has experience making such filters. They also dont have bio-wheels.
(for now,) I'd stick to the more common brands such as marineland or penguin....they're been put through years of use and have a lot of positive feedback.
I have the smartfilter for up to 55 gallons. it has worked great so far the only prob is after 6 months of use you have to do a complete tear down of the filter and clean all the channels out. was not to hard to do that just took some time. instead of a bio wheel they have there bio stars all the way to the right of the filter i think it holds 12. all in all id say it works pretty good. i like it.
Only problem I've seen with them is the cost of the media.... At least with Aquaclear you can rinse out the sponge, and with the bio wheels there are a lot of foam insert knockoffs that are just as good and cheaper than the marineland brand.