Apple has made Aperture 3 available an by all data it’s an upgrade worth buying. However, I and many other people have had the upgrade result in Aperture constantly crashing on launch with a dump of messages that are not very helpful. One poster noted that he spent over an hour with Apple’s usually superb technical support yet never had the issue resolved. i discovered a potential solution that worked for me in the forums at DPReview, the superb digital photographic site.

Here’s how to fix the problem and what you’ll need.
Your Aperture 3 serial number (full version) OR
Your Aperture 3 upgrade serial number and your Aperture 2 full serial number

1. Aperture should be installed but is crashing on launch. If not, this tip isn’t the one you need. Don’t trash Aperture
2. Open the Library folder at the root of the hard disk (not the library in your user folder). Then open the Application Support folder followed by the ProApps folder. In this folder you will find .id files that correspond to whichever Apple Pro Apps you have installed. Move the aperture and proapps .id files to your desktop, ensuring that they are gone from the ProApps folder.
3. Launch Aperture. Even if you’ve entered your information before you’ll need to do so again.
4. Enter your Aperture 3 serial number. If your install is an upgrade, you’ll be prompted for your full version serial number. This is where you enter your Aperture 2 serial number.
5. Register your software if you have not already had this happen (unlikely).
6. Launch Aperture and let it upgrade your Aperture library. Be patient, this takes a while for large libraries.
7. Accept or not to use the places feature (your choice).
8. Exit Aperture and relaunch it to be sure all is solid.
9. If you have other ProApps installed, now would be a good time to launch them to ensure that they still launch properly.
10. Run Software Update. At the time of this writing, there was already a slideshow patch posted. I expect that there will be more based upon the volume of issues reported with the 3.0 release.

Of course if you have no issues with your install or now that things are fixed, dig in, it’s a solid upgrade and an excellent product overall.