If your running Oracle EBS your probably aware by now that Oracle has rebaselined. I heard about this from Steven Chan's blog back in June I believe. (BTW, if you support Oracle Apps his blog is a must read IMHO).
So what does rebaselining mean? Well, Oracle regression tests their patches against a standard patch level... It would be impossible to do this for every conceivable combination. Since the July CPU has been certified against this baseline, then its recommended that you apply the patches as soon as possible.
What did that mean for us? Well, on top of the new baseline and security patches business requested an OTL (Oracle Time and Labour) upgrade as well. In total, that meant we had to apply around 70 patches. The first time you apply the patches it always takes a bit longer because you have to read through the patch notes, pre/post install steps and you usually hit problems which require some investigation. It took us about 50+ hours to put these in our first environment. That was approximately the LOE I provided. Tomorrow we start our stage environment and i'm hoping we can do it in 16-24 hours.
So far we have hit one post patch problem. If you are using autoconfig and applied patch 4489303 - TXK (FND) AUTOCONFIG TEMPLATE ROLLUP PATCH L (NOV 2005) (part of the rebaseline for 11.5.9) you may hit Bug 4891248. To resolve the issue you need a patch, Note:359703.1 has all the details.
Now we just wait for unit and user testing.. Since a number of modules have been touched i'm expecting problems.