massive get out clause, its 3am in London and I have been drinking
I have looked into pdf.js and semi implemented it however it was only really worth it for firefox users, other browsers generally had a better experience natively, not that I am ruling it out forever but at the time I went for keeping it simple.
Seeing others cursors would be great. I am using the ace editor and that does not natively suport more than once cursor atm, if I had more time I may implement it myself but to be honest it is not going to happen in the very short term.
behind the scenes it is just a fully instance of tex-live 2011 which should cover 95% of needs. For other packaged which are available I am hoping people request them for the moment and I install them, for obvious reasons I am wary of allowing people the ability to install global packages on my server.
On first name and last name, you are right not really needed, same goes for email confirmation. I have been planning on killing those for a while but just hasn't happened!