We're now into S4 of it. I'm enjoying it. That said, having been through six odd series of Breaking Bad, it's beginning to feel like overload. Still, it's the (16yo) boss that decides what we watch.
The Russian aspect of it is forced, but it's very much there in S4, and yet to be explained (it clashes with the novelty of the overall story-line in my view). Despite all that, I'd recommend going back to it, especially if you liked S1.
Casts cost, but I still think (I don't know) that it was relatively low budget, especially when considering the media attention it's received -- I can't remember a film that has generated so much comment for a long time. The likes of Bond films always generate media attention (froth, might be...