If you want to personalize user experience and store user's preferences, you need to uniquely identify the user. This is obviously done by user accounts, for which you need a registration, also called “sign-up”, process.
You should want to require as few things from the user as possible. That's why many services use e-mail address instead of username.
The most streamlined process I encountered so far was: enter your e-mail address and you're immediately logged in as an user. If you want to log in later, click on a link/button in the confirmation e-mail first. Then you'll be prompted to enter your password and maybe even an username.
You may require the user to confirm his e-mail address before he can start creating content. Until then there's only a sandbox or samples for him to play with.
It wasn’t easy for me to decide how limited the FREE version should be. Sure, I want users motivate to pay at least something, but I don’t want to oust them completely.
I hate few things in desktop apps, even I understand their purpose. I hate grayed out menu options, just because PRO version has it. I hate even more if the unavailable option isn’t distinguished at all and I learn I have to pay first only after I click on it.
I can live with some promo upon startup or closing the app, because usually I don’t do it too often. But only if it’s in a “polite” way, when I don’t have to hunt the closing window nor close automatically opened tab in my browser.
I like x day trials, when the app works fully, but my problem with trial versions is, that it has to write the start date somewhere, obviously, and this thing stays on my computer even after I got rid of the software, again – obviously, but after that it’s just garbage polluting my system.
I understand DRM solves the problem of crap residing in my computer, but I hate it nevertheless, because it usually means even more crap in my mailbox.
So, what DO I like? I like when the only limitation is I can’t finalize my work (export, render or save), but otherwise I’m freely able to do anything the program offers. After purchase there is an encrypted file with a license key and this way I do it with QetriX apps.
And some polite ads for FREE users, even many of them know how to block them. I believe users can live with tasteful and just slightly disturbing (not by contents) ones.