Those Catadioptric Maksutov lenses may be a good buy, but, as raymo said, just don't expect the perfection.
I have something similar (
MTO-1100A) and I am happy with it, but, having said that, I needed to do some repair, to improve the performance,
see thread here, #8..
However, it is quite good for visual (lower magnifications), as it is very portable.
I also used it to take photos of Total Solar Eclipse in Cairns last year.