Performance drop after upgrading to 8.4.4?

Hi,
I was doing some benchmarking while changing configuration options to try to get more performance out of our postgresql servers and noticed that when running pgbench against 8.4.3 vs 8.4.4 on identical hardware and configuration there is a large difference in performance. I know tuning is a very deep topic and benchmarking is hardly an accurate indication of real world performance but I was still surprised by these results and wanted to know what I am doing wrong.

Hardware specs are:
2x Quad core Xeons 2.4Ghz
16GB RAM
2x RAID1 7.2k RPM disks

Relevant Postgresql Configuration:
max_connections = 1000
shared_buffers = 4096MB
temp_buffers = 8MB
max_prepared_transactions = 1000
work_mem = 8MB
maintenance_work_mem = 512MB
wal_buffers = 8MB
checkpoint_segments = 192
checkpoint_timeout = 30min
effective_cache_size = 12288MB

Results for the 8.4.3 (8.4.3-2PGDG.el5) host:
[root(at)some-host ~]# pgbench -h dbs3 -U postgres -i -s 100 pgbench1 > /dev/null 2>&1 && pgbench -h dbs3 -U postgres -c 100 -t 100000 pgbench1
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 100
query mode: simple
number of clients: 100
number of transactions per client: 100000
number of transactions actually processed: 10000000/10000000
tps = 4612.734318 (including connections establishing)
tps = 4613.308264 (excluding connections establishing)

Results for the 8.4.4 (8.4.4-1PGDG.el5) host:
[root@ some-host ~]# pgbench -h dbs4 -U postgres -i -s 100 pgbench1 > /dev/null 2>&1 && pgbench -h dbs4 -U postgres -c 100 -t 100000 pgbench1
starting vacuum...end.
transaction type: TPC-B (sort of)
scaling factor: 100
query mode: simple
number of clients: 100
number of transactions per client: 100000
number of transactions actually processed: 10000000/10000000
tps = 2799.134267 (including connections establishing)
tps = 2799.451407 (excluding connections establishing)

Any input? I can reproduce these numbers consistently. By the way, I am a new postgresql user so my experience is limited.
Cheers,
Max