None at all really lately. Since e-mail is well established, clients are sophisticated these days, and IMAP/SMTP servers hint their settings to the clients, and they autodetect most of the stuff. What users need to know are hosts for those servers, and e-mail providers advertise them clearly for their new users. In case of Diaspora it's not really very different. User registers on any server and there are no clients to set up yet, since it's site based (so far). In the future Diaspora can get more standalone clients too though.

I can agree that e-mail is fairly old, and over the years many things were ironed out. Decentralized social networks are new. It's not a reason not to develop them. Anything new can have rough edges to work on and things will improve. Arguments like "it's too difficult no one will use it, do it whatsapp way" are bunk and not a valid reason to avoid decentralization. The point is how to make it easier to use while not sacrificing security, privacy and users' control.

If you aren't - it's completely up to you. No one is saying Diaspora is the only service to use. Still there are a lot of those who are target audience. A lot of non technical people join diaspora. So you arguments don't stand. People who value privacy, don't like their info exploitation and etc. come to Diaspora for these reasons. Many of these people are not technical, yet they resent Facebook and co. who strive on peoples' cluelessness about these matters. Whatsapp strives on exploiting perceived convenience (fake one) while selling to people insecure and crooked service.

Sure, what else can you expect from a young network? Any new network starts with people you aren't familiar with. It grows over time. It's simply wrong to expect Diaspora to be Facebook clone while coming there. Know your expectations and know the differences. Diaspora is great for what it is - content discovery, discussions about your interests and etc. through decentralized social interactions. You are not going to find all your school friends after coming there if you expected that. Of course those who come are free to invite their known contacts there as well.