OK, I gave it a chance for a few days to check it wasn't my prejudice, but bubbles are now off my prefs for good.
A number of the ex-thereians amongst us have told me how they hated them. Now I understand why...
Even on a one-to-one, it can be hard to follow the flow of conversation and to figure out which reply is directed at which comment. In a group, it's impossible to tell who is responding to who and why. I have noticed that the "still-bubbled" tend to be a lot quieter. So all in all it's a chat-killer.
Unfortunately, the inevitable counter-argument that "well, you can always turn it off" doesn't wash, since you never know whether you are chatting to a bubbled person, someone who is at a definite chat-disadvantage.
My main argument is that that this "feature" is therefore damaging to the overall community.
The "bobbling titles" resulting from this change even when you have bubbles turned off are just an annoyance, but a step back nonetheless.
The incredibly sensible (dare I say obvious?) idea of putting your title on a separate line to the name is the only step forward.
OK, my rant is over.