vacuum in pg9beta4 much slower than in 8.4

I think this is ok, but I'd just like a confirmation.

I have a db cluster with 6 databases, totaling around 6 GB of data.

In postgres 8.4 subsequent runs of 'vacuumdb -afvz' takes around 55
seconds (average from 10 runs). 'vacuumdb -avz' takes around 40 seconds
(average from 10 runs).

However, in postgres 9.0beta4, 'vacuumdb -avz' takes around 2 minutes
(average from 10 runs), and 'vacuumdb -afvz' takes around 12 minutes
(average from 4 runs).

I understand that VACUUM FULL in 9.0 copies all the data, but is it OK
that plain vacuum in 9.0 is slower than in 8.4?

Mike