My installation of ATT is currently using 199.32 MB, is this normal? I've asked several others in my guild and they are sitting between 8-16MB of usage.

ATT uses roughly 180-190mb when you first launch and will slightly go up as you add more items to your wow cache (relogging clears). The 8-16mb usage they reported are from other addons that do a lot less work and calculations.

ATT uses this much memory because it stores the database on the local machine. If we didn't do this and relied strictly on the Blizzard API memory usage would be lower, but every time you got an item you'd experience a 5-10 second freeze that would do nothing but cause frustration.

I believe Crieve is going to see if it's possible to "shrink" it further, but the problem is LUA is restricted in how many local variables you can use which causes a problem with all the things that need to be tracked

Thank you very much for your timely reply!! I've noticed that last week or so that the longer i'm logged in, the more stutter I feel when mousing over any item in my inventory. It got so bad last night(so much so that my UI would completely disappear) that I had to quit the game and relaunch. Has this been reported? If not, would it be beneficial to report?

Feel free to report it. When you do, and if you don't mind, list any other addons you have. The reason for this is a lot of addons do various calls and increase stuttering over time. A couple off the top of my head are TSM / MogIt. So seeing what addons you use can help us in seeing what might cause it and if it's something on our end we can fix or if it's another addon.

Also, do you notice the memory going up for AllTheThings? As you play items are slowly added as you accumulate more into your cache. Personally I haven't seen anything after extended periods nor has Crieve who uses ATT plus base. However that doesn't mean it can't be an issue with ATT still and something we can look into to see if it is. It's always possible another addon may use "dirty code" and interacts with other addons badly. One that is notorious for this is TSM because it basically attempts to rewrite the entire UI and tries to force addons to run through it which can cause taint/errors.