Why would anyone pay for 3G when you can just tether it to you're jailbroken/hacked phone?? I assume most of us on here being the techie's we are, pretty much know/have the ability to do so without paying the monthly fee. I for one would not pay for 3G primarily because I don't game on my PSP more than a few hours a month anyway....some of you probably take the Tube/train everyday, then I could see the need for 3G. But again, why pay??
I believe when will need to install an update when you power on the Vita for the first time. You had to download it for the 3DS even.
No. you don't need to update, but if you use any PSN features, it will force you to update or you can't get into PSN messenging, PSN Store, and other PSN stuff. You can still play PSVita games if you don't update. If they check the internet (you have it on) before playing, they may tell you to upgrade, but you can't always turn off the networking features to bypass the check.