I personally feel that you should be able to do whatever the fuck you want with your consoles/handhelds, but the last thing you want is to get your account banned from hacking. I agree that it should have been a day one feature though, but we should all be used to Sony making these stupid mistakes
You have to do it by using the remote play feature. It will show your PS3 XMB on your Vita with your PsOne games and you can basically stream play them onto your Vita. The PsOne games actually play beautifull on the handheld. Let me know if you need any help and I'll help you out.