I love WordPress and I obviously have it installed on my website and pretty much everyone I know who has a site uses it, too. However, there's one thing I don't like about it and it's the registration system. It's so limited! The only fields that are available are Username and Email. It would be nice if I could add more custom fields like Company or Website or Occupation etc. like when you sign up on this website.
Also, I would love the option of letting users choose their own password instead of sending them an auto-generated password. Again, this goes back to having more options on the registration system.
I know that there are plugins that do these but I don't like installing a lot of them especially since something like this would be a great addition (in my opinion ;) ) to the core WordPress files.