So as i promised here my observations.
Overall it seems to be slightly more memory efficient, a little quicker and slicker all in all and the battery also seems to hold a while in my case. I can run for almost two days on one battery charge when not playing and surfing too much (I have WLan and Data swiched on all the time so it uses what is available).
The only thing that bothers me a bit since the update is, that something seems to go wrong with the transition between WLan and HSDPA. The Phone won't stay on WLan when it 'sleeps' so it has to reconnect when i turn on the screen after some time - even though I turned the policy to never turn off wifi. And also sometimes WLan or HSDPA respectively won't connect correctly until i turn it off and on again... but this wont happen in a reproducable manner.
With no crashes, no SODs, stable and quick'n'slick it's the best Ive seen on the Streak.