I drove/tested the Cizeta and the Ferrari F40 last night (first chance I've had to play since the update). I found that there was no problem with either of them with snap oversteer and spinning. The F40 even seemed kinda easy to handle, considering all the flak its handling's been getting from some on this esteemed forum.
I was driving those cars stock, SH tyres, abs=0
The only problem I had was that with the Cizeta it seems like you have to start braking several weeks before the corner. I can get an appointment with my dermatologist more quickly than it takes the Cizeta to slow down for corners. Quite like that though - it's a lot of fun. Really nerve-racking!
I can't really give any before-and-after the update impressions though. I had only driven the Cizeta once before, and had never driven the F40.
So perhaps the improved-MR-handling speculation will contiunue. This is a mystery that will go down in history along with Atlantis.