3G 8GB OS 3.1 Battery always says 100 iPhone

Hi all,
Yes, I foolishly said upgrade to iTunes the other day, without checking the forums, that wont happen again
Anyway, been trawling things for a couple of days and am having one major problem with 3.1.
My Battery status icon always says 100%, then the phone will just flat line/freeze, no 20% warning, nothing, works one minute and then zip, nada, zilch the next.
I say flat line/freeze because Im not actually sure if its still there or not, but I cant get it to respond.
The only way I can bring it back to life is to hard reset it (power+home), then it reboots and says, 100% battery.
Until this problem is fixed, I have no idea if the battery life is even the problem and if it is, its certainly worse since going to 3.1, but thats not news from what Ive read.
what have I tried?
2 separate restores, both of course to the now infamous 3.1 upgrade.Powering the phone off and leaving it to charge for a while, says it charges, but again no updates on the battery status and truly random as to how long Ill get out of it, always 100% battery.A hard reset (power+home) while docked, did some weird stuff, drew a line horizontally across about 2/3rds of the way down the screen and then the whole thing went yellowish then white, had to reset again, while not docked. Came back.
In summary, Ive abandoned my iPhone till theres a 3.1.x update, because I cant trust the damned thing to work
I could live with slow downs or even the odd reset but just flat lining means youre not sure when or where its going to happen, very frustrating.
Id like to have rolled back/downgraded to 3.0.1 but from what Ive read, this isnt a true 100% rollback and that pieces of your firmware are left at the newer levels?
So I wonder what will happen at the next upgrade/patch from Apple?
Will it complain about mismatches in the phone or simply upgrade everything?
Ive seen the various sites around, with peoples ways to hack it back to 3.0.1, and Ive also seen the set of posts with associated rollback problems...
I dont care about Jailbreaking my iPhone and in all honesty would rather not have to hack too much in getting it to work.
Apple has turned my beloved phone-toy into a brick and seriously rocked my faith in their ability to release decent software. In an ideal world Id like a legitimate fix from them or an option to rollback/downgrade to 3.0.1 ...
Please, these are not hardware issues. Everything was going fine, till Tuesday, when I did the software upgrade.
Can anybody suggest other ways to fix the battery status?
At least then I might get an idea when its dying?
Assuming that chewing through my battery is the true underlying issue...
Thanks in advance for any helpful advice.
Phone info:
3G 8GB Factory unlocked, ~8 months old, never a problem till the upgrade.
iPhone 3G 8GB iPhone OS 3.0.1