It's funny what you say about ABS. I print with it 90% of the time on a CTC clone very similar to this machine and have virtually no problems at all. I have enclosed the printer
Abs works on enclosed printers, mainly because the whole model cools and shrinks at the same rate. In an unenclosed machine each layer shrinks and cools at it's own rate, so even when the model prints, it's weak and the layer binding is poor.

To be honest even if I had an enclosed machine I wouldn't use abs (it would be great for polycarbonate and nylon). It smells horrible and you end up using a lot of acetone. I just find pla and pet-g to be better all round. Plus there are so many new and amazing materials around that There is no actual necessity to use abs.

Torby - do you have a print area cooling fan ?
That would help with print appearance a lot.

Plus I've lost track - is your print area enclosed or not ? :-)