Apart from the air quality, Warsaw is great for cycling. It ain't hilly and there's enough bike lanes. Also Veturilo is pretty good with its dense network, especially in Spring before the bikes start breaking :)
Agreed about terrible air quality in winter. As to "great for cycling", I think it has a long way to go — there aren't that many bike lanes and there are parts of the city which are split by huge car-only high-traffic moats. But it isn't terrible either!
