A couple things..

[JWH_Matthew]

Is their currently a cookie that you could use outside of the admin to see if an Administrator is logged in? I would
like to create a plugin that would replace any content with the text editor if the admin is logged in. Allowing
users to browse the site and make quick changes, this will allow them to see the theme along with the content when
editing. At some point I would also add a top bar that would have options like create page, delete page, save page, logout,
more..

Second Question, What would it require to make GS run on PHP 4.3 I have a client who loves Yahoo small business hosting
which only has PHP 4.3. I would be willing to run an older system if one exists..

Anyone made any headway on a multiple user system for the Administrators?

[spilarix]

1 - There is a "view button" to see your modifications in admin.
A complete integration of the admin in the front would be probably a big work and it would be not necessarily better than the current admin.
However, it could be possible to create a plugin to do some admin actions.

2 - It requires to rewrite GetSimple ;-) You can just hope a migration of Yahoo to Php 5.

[Zegnåt]

Is their currently a cookie that you could use outside of the admin to see if an Administrator is logged in?

No there isn't, though I can't say I remember why Chris didn't include it. I guess it's just not how GetSimple was build to work.

What would it require to make GS run on PHP 4.3?

It would require a server update. GetSimple uses SimpleXML for all its XML-file management, editing and reading. This PHP extension is not available for PHP versions lower than 5.