we have 3 nodes:

2x sles 10 sp3 + oes 2 sp3 (32 bit)
1x sles 10 sp4 + oes 2 sp3 (64 bit)

a) Do you have any experiences with problems that could occur with such a "mixed mode"?
b) Any lessons learned on migrating all servers to 64 bit?
c) Is it "dangerous" to migrate a clustered nss volume between 32bit and 64bit nodes?