I've had a bit of time to play with 11g lately. One thing that really jumps out is the directory structure.
In 10g, it was relatively easy. You had 2 folders created at the root, OracleBI and OracleBIData. Most of the server specific stuff (logs, binaries, etc.) are in OracleBI. Pretty easy to navigate. With the introduction of 11g and the integration with WebLogic, the directory structure has exploded. With that, the relative ease of finding files for the new guy or gal, is gone.
If you want a good overview of the current directory structure, read OBIEE 11g - Demystifying the directory structure by Jainnys (couldn't find any more information).
Now, the fun part.
The following group of folders is repeated no less than 7 times:
Here are there locations:
Note that this one is only one level below the previous.
Ditto for those.
Two levels below that top one...
Let's switch it up a little; go back a couple of levels and start drilling again.
Just a fun little observation. I would imagine there are legit reasons for this kind of directory structure...but I certainly don't understand it yet.