Looks nice!
And no 256 passes is not overkill at all. Sometimes interior scenes can need 2000-3000 passes to really get that final 5% , yes most jobs will be fine if you stop it after 500-600 passes, but it's like magic happens when you get several 1000 passes.. pixel size light bouncing etc.. its just stunning results, if you have the time and the computing power!
biggest hurdle for Corona so far in max at least, is the memory consumption.. rendering 2 - 2.5 K images is easy, but doing 5-6K renders is quite painful on 32GB (even 64gb sometimes) ram machines.
anyway, slightly off topic :) keep it up! looking forward to a new maya release with a bit more interface, as im fairly new in maya.