I find Keynote 6 in Mavericks to be both a step backwards and a step forwards from Keynote 5. It has some neat new transitions and all, but the iOS-ification (simplification) of the interface, as well as the removal of some key items in the Export to Quicktime command (can't set the exported movie to loop; exports into .m4v format, for instance,) make me want to throw it in the bin. What I am most concerned about, however, is that once Keynote 6 is installed, it appears to hijack the launch services app/doc binding.
When I click on a Keynote document, (version 5 or 6,) Keynote 6 opens as expected. If I 'Get Info' on a Keynote 5 document and use Open with: to select Keynote 5, (either by selecting Keynote 5 from the pulldown list, or by choosing Other... and selecting Keynote 5 from within the /Applications/iWorks folder, that document will open in Keynote 5. This is normal and expected.
Disturbingly, the Change All... button, which is supposed to set the app/doc binding for all .key files, does no such thing when I set a doc to Keynote 5! No .key documents open in Keynote 5 after I execute this command.
Even more disturbing is that at some random time, the specific .key files I individually associated with Keynote 5 will lose this association and revert to opening in Keynote 6!
I've rebuilt the launch services database, verified permissions, etc. This was happening before 10.9.2, as well. I'd like to keep Keynote 6 installed, but it just doesn't seem to play nice.
Any flashes of insight as to why this is happening?
SOLUTION
After installation, move the new iWorks apps onto another volume. This prevents the Launch Services 'hijacking' from occurring, allows the use of the new apps, and shuts down the inane update request from Software Update. I've tested this on three separate Macs, and use a Time Machine external drive as the repository for the new apps. Laptop users without perpetually mounted external drives may wish to add the apps into a disk image and mount the image only when needed.
This solution provided by user benwiggy at Mac OS X Hints.
ADDENDUM
With the release of Yosemite, this problem now recurs. Putting a bounty on a REAL SOLUTION!
Best Answer
I don't have a complete answer, but I have seen this as well - as long as Keynote 6.x is installed, I can't set the Open with... to Keynote 5. I've been deleting Keynote 6 from Finder, but unfortunately it comes back every time a Software Update is performed, so it's only a partial solution.