I have built the Zvezda BT-5 and also have their ISU-152 which I haven't
built yet (Both are boxed under the Italeri label, but are Zvezda mouldings).
I found the BT-5 fairly straightforward to build, but did have a problem with the fit of the front mudguards (can't remember exactly what the problem was but I fixed it eventually). The independent track links
were tedious to assemble, but rubber band tracks really wouldn't have looked right for a BT-5, it has very distinctive
long track links.
Overall I'd say that although they are not as well-moulded or easy to build as Tamiya
or Academy, they certainly aren't bad, and offer a very interesting selection of Russian armour
at reasonable prices.