I would say it is pretty stable as well. Other than Adobe Flash crashing in Safari I have seen no real bugs.
Apple has done a fine job of tweaking the memory usage since DP 4.
I have a ton of apps open running full screen on my poor little MacBook Air and it is running just fine. Very fast and responsive.
Right now with 9 apps open...
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How much RAM do you have on your MAcBook Air ?
My Memory page for SL looks very similar with 6 apps open and I have 2gig, wondering if I am going to struggle