Is 512 MB RAM Really Enough for Android ICS? (Background: I never use ICS Phone, so i want to ask about performance)

Some of Android ICS Phone (e.g. Xperia J, Xperia Sola) has 512 MB RAM. How about performance of Android ICS Phone with that amount of RAM? Sony Developer Blog said that there is performance issue with only 512 MB RAM, but is it really matter to user?
I have an LG Optimus 2X. Same, 512 MB of Ram. I've used ICS. Now I'm on Jellybean(4.1- CM10).
 I've never had a problem using the phone. (Heck it because so much smoother in JB). The only problem is that certain memory hungry apps like Chrome are a tad bit laggy.