Ever since I started working for NorthScale (now Couchbase) I've done my very best to ensure that our stuff works on Solaris (if not I'd have a hard time doing any development ;), so getting it to work on SmartOS shouldn't be a big problem.
So far I've only been using the Sun Studio tools (I can't help it but I still find dbx superior to gdb...), but a few days ago I added a slave running SmartOS to my Jenkins cluster to see how much work it would be to get everything built with the tools and libraries I could install with pkgin. We do compile our software on different platforms and with different compilers, so I didn't expect too much trouble.
The "biggest" problem I had was to get libtool to stop trying to link 32bit object files into my 64 bit binaries. The workaround so far is to use:
CXX="g++ -m64 -L/opt/local/lib/amd64" CC="gcc -m64 -L/opt/local/lib/amd64"
This was a small goal for me, but it will really ease my testing of a full cluster :-)
Now that I've got everything built on SmartOS, OpenIndiana, Soalris 10 I guess I should create packages for pkgin, IPS and SVr4 :)