1 - I dont use skype
2 - no issues with picture sms as of yet, send quite a few though
3 - I use SBSettings to end any processes, infact I have more memory becuase I have more control over what to end and what not to end
4 -Battery is the same to me, might be a little worse but cant say I've noticed it and Ive got loads of apps
5 - Never had a problem as of yet but hey thats the risk I take, you need to know what your doing but if it does mess up, I will restore it, and if I cant restore then I say I lost it and claim on insurance which is included with my contract
Im happy with my jailbroken Iphone, pay for all apps, dont use installous or sinful iphone. I like having fuctions on my phone that any other phone has straight out the box.
Its your choice at the end of the day, make your own mind up. everyone will have a different opinion