I heard of problems about Solaris 10 not liking to share a swap partition with Linux.
Solaris is using a slice to swap, while linux is using a primary or extended partition for it, so by default they are different.
There should not be a problem to tell linux to use the solaris slice for swapping, if you really want to save disk space.
However, I think linux want to have some sort of formatting done on the swap partition before it can use it.
Solaris and Linux are both using the same partition ID (0x82) for Solaris (Primary) Partition and Linux swap, this is causing problems with a few Linux distros that wipe out the Solaris partition at installation time (e.g. Mandrake).
This is resolved with Solaris 10, that by default is using a new Partition ID (0xbf ).