I keep using Zeam,
it works on Froyo and Up so it works nicely on mimicry, cm7 etc etc.
Simple and light weight, negligible ram usage (around 8mb i think), has all the features i need (swipe for dialer, swipe for apps etc)
Lets you disable desktop scrolling, animations, and app drawer animations ( again speed and efficiency)
It not customizable but it is efficient and battery life is my main concern.
Another nice thing is it works at Any DPI unlike adw and trebuchet which i find crash alot of your not on 160 or 240 DPI
**i do have Virtuous Sense rom i use on occasion like for road trips etc where its plugged so battery life doesnt matter. just because the UI is easier to navigate and has the nice features of the Giant weather forecasts, larger dialer, etc etc but thats really the only time i bother with the stock Sense UI ( its pretty but its soo heavy)