Hay as I also wanted something similar (name, email id, password, confirm password that all [no user name]). So google drove me here.

I read through all the suggestions in this post.

I am planning to use something like this in user name -

Name: xyz abc

Email id: xyz@abc.com

[Automatically I generate, do not display in registration form] User name: xyzatabcdotcom

Password: *******

Conform Password: *******

Will it have any side effect? 

Will it lead to any wanted result?

Need you guys suggestion on above approach.

If you follow our examples in this thread it should work just fine

Yes Matt. I am following proposed example in this thread.