SharePoint

My management had asked me to look into the possibility to edit and save MS Office documents stored on our Drupal based intranet without a need to save them locally and upload them.
Pretty much, I need to resemble a functionality that Office 2010 and SP 2010 have when it checks out files for editing and saves them back to the site without user needing to save it locally.

I am writing a proposal to a prospective client for a complete migration of their website from their classic ASP CMS to Drupal. For the most part, it will be a very straightforward migration using very common Drupal features. The only complicated part is the Sharepoint login. Currently, employees are able to use the website front-end to log into the Sharepoint portal. I only need to be able to replicate that feature and put it on the new site. So by no means does this need to be a complete Sharepoint integration.

so, i'm working with a very large software company called XXXXX - been a part of this team in some flavor of role for around 8 years or more, now evangelizing drupal as the be-all end-all solution for our knowledge management needs (amongst other things)

I recently received an email from someone who'd taken one of my lynda.com courses. He writes:

The company that recently hired me to redesign their website is asking about possibly using Sharepoint - while I am promoting Drupal. Is there any information about performance of webpages using Sharepoint versus those using Drupal? I found on the Microsoft website an issue about downgraded functionality for browsers other than MS IE. Any input you may have would be greatly appreciated.