Improve dump and restore time

Hello,
I am studying how to migrate our Production Database which is running
under PG 8.2 and we would like to move to PG 8.3
I have read that the only safe solution is to perform a dump and restore.
Our DB is around 6GB large.
I wanted to have an expectation of the migration duration and performed
it on a less powerful machine than the one we have in Production.
Unfortunately it took very very long time (around 27 hours!).
Are there best practices to reduce the migration time ?
Some kind of questions I try to solve:
- Is it better to use a compressed dump or not ?
- Should I use a kind of trick like reading dump file from network while
restoring on the machine to reduce concurrent I/O and so on

Any advice is welcome.

Thanks!