Did you install any new application before your last shutdown??
Cause once i was stuck in similar problem..Later on found that the new application was causing that issue...so removed it from safe mode and PC started working normally.
You will not notice any noise while playing music or some other vidoes....it can be only heard when you play video recorded with that phone....but somehow it stopped in my condition.My mini pro stopped generating such noise now which I bought around 10 days ago. I am not saying noise has gone...
yes that noise problem does exists...but you can notice it when you. play recorded video with maximum sound.APart from that theirs no problem at all.AFaik se is working on that problem so no need to worry about that problem.
Yes SE Xperia mini or mini pro have poor battery life .I have xperia mini pro and its worth for that price range.Battery life is average but not that bad too as every other android phone is having trouble with battery life.
Small screen wont be a problem for me and i am more into music, phootgraphy and browsing.I dont like to watch movies on mobiles so i think SE sk17i will be a right choice.
Thanks for the help guys.