As Total-MAdMan said, spaces in file / folder names is only an issue when using the command line (but there are ways around it). If you are using your distro's GUI file browser you will not have a problem.
As for upper/lowercase names, Linux doesn't have a problem as such...
Some users have a problem (again from the command line) because Linux is case sensitive.
If you try to change directory to a folder called Documents
This would work:
This would not work:
The wonderful thing about Linux is choice. There is a wide selection of applications for almost any task, if kate is the best text editor for you then use it.
I know that vi/vim can be scary, however, I would suggest taking the time to learn at least the basics of vi/vim. It is the one editor you can pretty much guarantee will be available on any UNIX or Linux system.
The following site provides a pretty good overview of vim:
I personally almost always use vi. That doesn't mean it's the best editor, just the best editor for me
I suggest that you try a number of text editors and stick with the one's you feel most comfortable with.
For simple stuff: GEDIT, Kate, pico, JOE
For web design: Bluefish, Quanta+
For modifiying .DOC files: OpenOffice Writer (Part of the OpenOffice.org suite)