Any issues after upgrading from Yosemite?

Not for me. I run IntelliJ under Java 6 due to the discrete GPU issue though. Yosemite wipes out any Java 6 install but leaves Java 7 and 8 alone. I had to reinstall Java 6 after upgrading. I've been developing web apps under Java 7 without issues.

I am not so lucky as Charles. After upgrading, IDEA crashes every time I try to run it.
I haven't noticed Yosemite wiping out Apple JDK 6.  Usual "/usr/libexec/java_home -V" results with:

1.8.0_25, x86_64:    "Java SE 8"    /Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home
1.7.0_71, x86_64:    "Java SE 7"    /Library/Java/JavaVirtualMachines/jdk1.7.0_71.jdk/Contents/Home
1.6.0_65-b14-462, x86_64:    "Java SE 6"    /Library/Java/JavaVirtualMachines/1.6.0_65-b14-462.jdk/Contents/Home
1.6.0_65-b14-462, i386:    "Java SE 6"    /Library/Java/JavaVirtualMachines/1.6.0_65-b14-462.jdk/Contents/Home

But maybe Yosemite install removed something from Apple JDK 6 and that's the reason IDEA crashes. Will check it once I get back home.

PS As far as I know IDEA + Oracle JDK = terrible font rendering (aside from forcing discrete GPU, as pointed out by Charles), so Apple JDK 6 is a must I'd say.

I am on a mac and had the same issue.

Re-installed the mac 1.6 jdk at http://support.apple.com/kb/dl1572 and it seemed to do the trick.  

I also have 1.7 and 1.8 installed on my machine and those were untouched.

Yeah, been playing with different versions of Apple JDK and found the same one working for me. I wonder why it is not available from Downloads for Apple Developers, as previous versions. Additionaly, Java for OS X 2014-001 is not "Developer Package", so no sources available (in case someone needs to maintain "legacy" applications).