Using auto-commit OFF for transactions - instead of BEGIN

Hello

I ported a relatively simple application using Oracle 8i with a JDBC client
to PostgreSQL 7.4 with the same JDBC client, and everything just worked!

One thing that did come to light was that PG offers a proprietary 'BEGIN'
statement as a means of controlling transactions.

With Oracle, I was used to setting auto-commit to false at the start of a
transaction, and then calling commit or rollback at the end.

Is it safe for me to continue setting auto-commit to false for transactions,
and are there any compelling reasons - significant performance gains,
perhaps - why I might want to consider adopting PG's 'BEGIN' statement
instead?

Many thanks in anticipation.

Harry Mantheakis
London, UK