We always go in late August to mid-September and CSR is our resort of choice. Yes, the bus service is good all year round. We love the transportation compared to other WDW resort stays, even some of the deluxe resorts.
Now and then you may have just missed a bus and have to wait for another, but long waits are not the norm. At every resort you can get the scenario of six busses coming by and not the one you want, has happened to us at CSR too but not very often. The AK bus frequently makes a Blizzard Beach stop, but no resorts sharing a bus with CSR.
Since CSR has only four bus stops in a set order it doesn't take as long as at some other moderates to make the rounds and head out to the parks.