the cons are that betas are full of bugs and not all the features are enabled in 5.0 beta...
to register your ID you need a registered Dev to add you to the list of devices so you can install the os...
or pay 99 dollars to have your own dev account where you can save up to 99 devices to be allowed to use the betas..
plus side is if your not really a dev then you get to have all the new features... well most of them, but it is a beta and it is full of bugs so be warned