Will upgrading to iOS5 slow down my iPhone4 like iOS4 did to my iPhone3 ?

It may.

My iPhone 4 is OK. I upgraded to IOS5 last night and I haven't noticed any slowdown. I don't know if it is any faster. I also haven't had the problems with text messages disappearing etc. My only problem right now is that my calendar has 2 of every event. Not sure what I did to cause that to happen, but it is minor as long as I can fix it soon. I am going to spend time this weekend figuring out the syncing thing.

If you upgrade, I would recommend taking it one step at a time. First back up/sync everything to your computer, then download IOS 5, then, when it's done, upgrade. Let it go a long time. It took a very short time to put IOS5 on the phone, but a long time to restore all my files (which it did automatically) to my phone. You just have to wait until it is really really done.

k4k

You will be fine. My 3Gs was just as fast under iOS5 as it was under iOS4.

As the previous guy said tho, be patient once the update is done as it will download all your apps and settings again so you might want to put it to one side for a little while.

My iPhone 4 is running fine, even a little faster actually.

Made mine quicker, eventhough my events are doubled on my iphone and my calendar on my computer is blank??

Not in my experience of two days...

Mine sure did. Amongst several other problems. If I can go back to 4.3.5 I will.

I haven't noticed any slow down with my 4

My 3gs seems to be a little faster on IOS5 than it did on IOS 4

I updated mine on wednesday and haven't had any problems. Early benchmarks show a significant speed boost, especially in things like web browsing, in going from 4.3.5 to 5.0 and my experience so far bears that out. It is a bit snappier than 4.3.5 was.

I have had a lot of problems when upgrading my iPhone 4 to IOS 5. Very slow with many applications, particularly Messages and Phone. Messages will often hang or just return to the home screen. Phone will sometimes hang when calling someone. Wish I knew how to improve performance as the changes in IOS5 are good but if I had have known what I know now I may not have upgraded. If anyone has had this experience and was able to fix I'd love to know. Thanks.

I upgraded my iPhone4 to IOS5 and noticed that it was VERRYYY slow when I pulled up the phone or messages. It also hung a bunch in certain apps. Synched again and turned off the "backup to iCloud" and am now backing up to computer again and the speed improved dramatically. The cloud thing may not be perfect yet but IOS5 is still good.

It was probably syncing again that did the trick. I've noticed no differences from having backup to icloud turned on.