For all the great features added to SharePoint 2010, it is still mind boggling to see what issues remain with the user experience. Take this recent experience with SharePoint 2010 slide libraries. Terry turned me on to this in his instance so I began a validation in my instance. My instance is currently patched with the October 2010 CUs.
I published a PowerPoint presentation to a slide library in SP2010 that had “require check in/out” enabled. All slides were published in a checked out status. I needed to check them in. No problem, select multiple slides with the new “multiple selection” feature and check in.
Nope, can’t do it. Security issue? I’m a logged in as a site collection administrator and I’m in the Owners group that has access to the slide library. Shouldn’t have a problem there.

Okay, let’s see what happens if I don’t select multiple slides.
Nope, tool ribbon is still disabled. Even tried enabling “protected mode” in IE for trusted sites (in which this site resides).

Do I have access to check-in from the drop-down? Yes.
Does it work? Yes.

Now the special triple click trick. Click the disappearing drop-down button. The context sensitive drop-down list appears. Click it again and the button disappears…but the drop-down list remains. Click again and the drop-down list disappears. Ahhh…the wonders of Ajax. But I digress.

Let’s take a look at this problem from an SPD perspective. We can see the files that are checked out.

Let’s select three files and check them in.

After performing a check-in, we still see the “checked-out” checkmarks. Even the context-sensitive menu is confused about whether these slides are checked in or checked out.

Perhaps it’s that nagging problem with SPD where it doesn’t refresh correctly. Press F5. No change.
After closing and reopening the site in SPD. No change.
From the browser UI I validated that they are still checked out. Another non-functional feature?

It looks like SPD continues to be confused as to the status of the slide, even after closing SPD and starting a new instance.

SPD shows the same slide as checked out. No amount of F5-ing changes this.

Hey, let’s try to use this feature to allow us to “manage files which have no checked in version.”

But wait! There are no checkboxes with which to select the items?

Perhaps I can use the “select all” checkbox.
Nope. The "select all” checkbox is non-functional. What’s up with this?

Oh, and this appears to work just fine on a document library in the same site.

I’m certainly open to others’ experiences with Slide Libraries in 2010. Perhaps the Dec 2010 CUs will help?
As another test I went into SPD 2007 and tried the same thing. No check-in will occur from SPD 2007. So, I guess they didn’t break anything.

References
SharePoint Slide Library Adding Functionality