Trust me. If Linux really eats your RAM to the point of reaching an OOM state you will know.

(This was of course because of having too many apps relative to my RAM. Not because of disk caching.)

The OOM behavior is not pleasant for a desktop system.

And this (the OOM behaviour instead of the paging behaviour on linux) is something that can (and should) be criticised. Every time I encountered a situation where I was running out of memory (usually due to some out of control process) the system would become completely unusable. All interactivity is gone, so it was impossible to kill the out of control process (which was typically misconfigured program i started). If the OOM killer started to take action it would almost never kill the process that was gobling up memory like crazy but instead any of the other apps that are necessary to intervene (like e.g. the terminal or the WM). It always seemed incredibly stupid to me.

I remember some time back there was discussion about improving the OOM killer, but I don't know what came out of it.

I've heard some good results with it and the applications locked in memory is configurable.