7.4 <-> 8.0

All,

Couple questions from to a recent upgrade from 7.4.8 to 8.0.3. With
servers for both versions running on the same machine,

pg_dumpall -p 5432 -c | psql -p 5433 template1

appears to have migrated the databases smoothly. At least I didn't
notice any errors in the process, and all the data appears to be there.

The one troubling thing is the new 8.0 databases take about half the
disk space as the 7.4 databases. Similar dump | psql to recreate the
databases on other machines running 7.4.7 and 7.4.8 show the same thing
- the fresh copies take half the space of the old. What might be
happening with the old db, so it takes so much more space? Could half
the data be missing?

What's the best way to move data from 8.0 to 7.4? The 8.0 pg_dump
writes a dump that doesn't restore with 7.4 psql, and 7.4 pg_dump
doesn't seem to handle an 8.0 database. At least I haven't found the
right switches...

Thanks,
warren