Postgres && GIS

I am exploring the possibility of using PostGreSQL for GIS applications
(as I am sure many have before me) and am wondering if there are ready
answers to a few simple questions (the FAQ seems still in it's infancy):

- there are geometric types described in the documentation, is anyone
making substantial use of them and the query tools described also? if
so, for what purpose and using what as an interface layer?

- is the JDBC interface compatible with the geometric types? could it
return a polygon if that was the result of a query, and what would it
look like when returned? conversely, how would one insert a polygon into
a database? it is something I haven't wrapped my head around yet, how
one would insert several hundred vertices of data into a dbase using
standard SQL. Just a great big well formatted text string?

Thanks for your help, I'll try and compile for future generations, of
course.

Paul Ramsey