I am considering the use of PostGres in an app that is barely gotten started. So there isn't really any legacy code to deal with. When it comes to Postgres is there anything one needs to watch out for ? Especially since most of my guys have SQL Server background.

Not a thing I can think of. LLBLGen works just fine with all supported DBs. Postgres is a good one. My advice is that you should use Adapter template set, as that is most suitable if you decide you move to another DB later.