Is there a concern as far as memory when running ICS ROM on 512MB device (DroidX) Based on available evidence so far, are there legitimate concerns that people with older phones that have 512MB memory (e.g. Droid X) would experience memory issues when running 4.0 (Ice Cream Sandwich) based ROMs?

To be more specific:

If my stock Froyo 2.2 ROM boots up with ~170MB memory free, and during my day to day use I end up with ~50-70MB memory free (this is with ALL my actively used apps loaded, and Android not killing any of them to make room for others), what would the expected memory footprint be on an AOSP based ICS ROM?
If there is a ICS ROM available for the Droid X, it should run on a device with 512MB. The minimum requirements for ICS specified by CyanogenMod team is 256MB and a "decent GPU". I am not sure what kind of GPU the Droid X has, but you will probably have a better experience with Gingerbread then ICS on that device if the GPU isn't that great. My brother had that device and complained constantly about lag and lock up. If you have the "stock" MOTOBLUR, you will probably have a better experience just by installing any AOSP based ROM.

You can expect the footprint to be about the same, maybe a bit less, then what you see now. This is because the android OS will always try to use as much memory as possible in order to try and keep your experience better. If the application is in memory you can switch back to it faster then if it has to reload the entire application, plus it can "remember where you were".

As a side note, I don't currently see any CyanogenMod 9 builds available on the CM forums for the Droid X, but that doesn't mean that there aren't any, I just don't see them.