Hey guys! I just got my Droid X about a week ago and one of the first apps I got was ATK. I noticed that when I first turned the phone on, the memory was at around 220. I killed all the apps (other than ATK of course) then it jumped up to around 255. The longer I have my phone on, the more memory it takes (ie My phone has been on for about an hour or so and it's down to 85 before I kill the apps, 100 after).
If this helps at all, I just got the 2.2 update.