Interesting, just a week too late for me... I found
Aigner to have a good website with well taken pictures and easily readable layouts of all flats on offer but not a huge choice and mainly at the high end.
Immodium Scout is full of crap, lots on offer but the descriptions are poor, often uninformative and the agents sometimes unbelieveably unprofessional. Still the world and his dog are selling on this site and there are tonnes of ads. In the end I found my flat through
Planet Home which is an OK site, neither totally perfect nor a waste of time. They do have a lot on offer, and the descriptions are OK. This thread will probably get modded onto another as it's not a new topic but I can add more details when I get a bit more time.