In installing Kubuntu 15.04/P5, which file system should I use?

[RLynwood]

I used JFS in installing 14.10 because I didn't see an option for ext4. I couldn't decide on the spot whether to use JFS or XFS and just chose JFS. Can someone explain why ext4 wasn't an option and, if that's the norm, which fs I should use? Also, can an installed fs be changed, i.e., can one add one, then delete the first?

[claydoh]

In the partitioner portion of the installer, scroll up or down in the filesystem dropdown list to see ext4 - it is probably the best, safest, and most supported for most users - though ext3 may be considered the safest choice by some as it is is better on very old hardware.

You cannot change the filesystem of your root partition ("/") without wiping the data on it, in most cases. An exception is ext3 and ext4, as they are directly related to each other.
Well, I am sure that one can, but it is likely very difficult and danger-prone.

[kernelbasher]

ext4 is still my choice
I know many have started using XFS on /home