Individual shot may be quite noisy... the noise level will be affected by temperature as well (warmer the camera sensor, higher the noise, and the dependency is exponential with the temperature)..
But it should be averaged out in stacking process.
"banding" (this is caused by camera circuitry) is also supposed to be random, so it should average out (so that means, more sub-frames, the better... 10-15 sub-frames should ne adequate, though).
EDIT:
Have a look at this:
http://www.iceinspace.com.au/forum/s...ad.php?t=37039
this was taken with Canon 400D at ISO 1600.