This is clearly a well known and unresolved problem Samsung have allowed to continue. I bought my Galaxy S2 just on four months ago and everything has been great until two days ago when just as most here have described, the unit started heating up very noticeably and the power was drained within three hours.
I bought the Galaxy S2 because I believed all of the positive language on the net about the phone, but now that I have spoken to three different people at Samsung Australia, all to no avail, and three people at JB HiFi (place of purchase), I have been reminded that just because people are willing to spend time with you when you spend doesn't mean they will do anything at all to help when things malfunction.
JB HiFi in Perth's EnEx100 arcade told me repairs could take up to two MONTHS, irrespective of the fact that I won't be in Australia in one month. Samsung told me this was the first they had heard of this kind of problem and that I must drive something like forty five to fifty kilometers from home to drop it in at their service center where I would need to allow two weeks on average, but it could take a month, because they have no idea what the problem is likely to be.
The 3rd person at JB HiFi to take a call from me did recognize the problem and said that resetting the unit may help. It hasn't - but at least she admitted to having seen the problem before and had an idea for me to try for myself before asking me to go phone-less for two weeks to two months!
Samsung have let the ball drop on this and I will wait to buy my next phone from some other company. Silly thing is, if they'd spoken to me reasonably and as though they gave a damn, and resolved the problem, I would have continued thinking about the Galaxy S3 as a possible near future purchase as well as a Samsung pad in a month before I move overseas again: Two lost sales for Samsung.