Strange, I'm 99% sure there was nothing else changed (hence being a minor version change).

Someone mentioned:

We noticed this on one of our 3G iPhones, but a reset (as was suggested above) and a full charge sorted it out. Now battery use seems to be improved on our iPhone 3G overall.

http://discussions.apple.com/thread.jspa?threadID=2471287&tstart=0

well its braining the battery like nobody's business of my 3g, even o2 said they have had allot of problems due to the update

The update just adjusts the way the bars are represented, there are no other changes.

From Apple; "[the update] improves the formula to determine how many bars of signal strength to display."

major disappointment this update for me, drains the battery, given my sms sending problems, should have just kept it as it was

It will do.

its done it now, took ages to get 4 bars then zoomed thro, iv restored it and synced it, now, and it says it 4.0.1 but it looks the same layout,

few mins for me as well. 10 max.

Only took a few mins to download to mine.

Took mine about 3 hours

iv backed up my iphone gone to update it and it goes to the time line saying "backing up "iPhone" but it goes to 3 bars then stops, its been like that for ages, how long does it take to download?