I've noticed an increase in lag when swapping out characters. This has been ongoing since the beginning of ddo, but seems more pronounced since U9.
Once I have switched a couple/three times, things get a bit hinky. It is especially pronounced during gear swapping and buffing/debuffing. Particularly items and spells which affect stats. After 6 or 7 character switches, or staying on one through a long string of quests, switching a stat item can freeze the game up for several seconds.
Obvious work-around is to completely restart client between character switches.
I also noticed this causing similar issues for people when stepping into particularly large quests and explorer areas. Many times stepping into the desert will cause a couple of folks to dc. Its not as bad as it used to be, but U9 brought some of it back.
A big upgrade on my PC really helped these issues for me, but it just prolongs the build-up of memory leakage.
A second lag issue is that it seems the nightly lag-thirty is back. I assume this is server backup time, but it is very scary because these are the times when you hear horror stories of people losing items by taking them out of mail/shared banks. All the vendors lock up a bit and mail/bank npcs basically shut down. It is no where near as bad as it used to be, but it is back. Usually hits around 2am pst.