Do you think anyone really knows the answer to that?
I am not having any lagging or hang-ups myself! 3GS is working great! I have been using it all day listening to music in the background, checking email, texting, taking some notes in a meeting, replying to some email. I am loving it!
4.0 was just released yesterday.
It'll most likely be another 2-3 months before 4.1 is released.
Now, there will be small 4.0.1...4.0.3...etc releases to fix any issues.
Just hang tight. I'm sure Apple is already working on the next OS update.
My wife's 3GS is kickin ass! You need to restore or something.
My 3G on the other hand.... I gave up when we were 2 hours in to the "backup". Ugg... I'll just rock my 3.1.2 for 2 more days. It's jailbroke just the way I like it.
I've noticed serious lagging with any iPhone when I sync my my iPhone and Gmail calendar to one another using a subscription. Does this sound anything like your setup?
I can subscribe to the calendar and within a minute, my phone will take minutes for any app to open include Settings. I can delete the subscription and all is good.