I have library with 'require checkout' set that contains mpp and vsdx files. I have MS Project and Visio 2013 (SP1) installed locally.
If I choose edit for one of the mpp files, it simply opens in MS project as read-only and doesn't allow me to save it (only as a local copy). There's no option to check-out anywhere. Obviously I can check-out manually in SP before opening then check in again afterward but it seems clearly wrong that I'm allowed to click "Edit", make changes, but then be unable to save back to SP again (even if you switch back to SP to check-out, Project thinks you've opened it Read Only and won't let you save back to SP).
For Visio it's even worse - when I choose Edit for a vsdx file, it opens in Visio as though I can edit it, but when I try to save it says
"UPLOAD FAILED! You'll need to check-out the file before we can upload changes", and presents a "CHECK OUT & UPLOAD" button, but clicking this just gives the same error. Not only that, but the 'Check-Out' button on the Info page does nothing at all, I've confirmed it simply doesn't even send any request to SharePoint to do anything, and no errors are reported anywhere.
However...it seems the Visio problem was temporary and apparently connected to the fact that I have a problem with my internet connectivity status that means it sometimes shows
"No internet access" even when there is. But in fact my SharePoint server is on a LAN and doesn't require any internet connectivity anyway, so it's clearly a bug that Visio is simply ignoring any request to check-out just because my internet connectivity status is wrong.
Word/Excel/PowerPoint also have an issue with this but at least they tell you that they can't check-out because of this.