Will I be ok updating to Mavericks (using Aperture 3.4.5)?
Aperture 3.4.5 is working with Mavericks, that should not be a problem. Just take the usual precautions and make a current backup of your mac.
But you should check, if other applications or plug-ins you rely on, like scanner drivers, printer drivers, etc, are compatible with Mavericks.
I'm slowly debugging the lib (exporting sublibraries, reimporting all photos, etc), but it is a very long term project.
That looks like a daunting project. What kind of problem is there with your Aperture library? Have you tried all repair options? Repairing and Rebuilding Your Aperture Library: Aperture 3 User Manual
Thanks! I think I will go ahead with the upgrade to 10.9.
I started using Ap3 in the beta versions (early 2010), and since then the lib has grown to 30K items (mostly from Panasonic DMC-GF1 and GX1). It's a referenced lib, with masters on an external HD. Adjusting or deleting the earlier images is a little risky--the OS can go unstable and damage the file structure. I've had to use the Restore HD a few times when running DiskUtility. I think newer imports are not troublesome (2013 seems OK, maybe 2012, but 2011 and older can be bad). I constantly use the Repair functions, and the Rebuild as needed (I also keep the vaults updated).
I'm exporting groups of projects as new libraries, then I reimport all images/videos and delete the originals. I'm also temporarily flattening the keyword structures (but not sure I need to). Then I can import the clean sublibs into a new main lib. I'm about 18% done after ~3 months.