Well, never really looked into it, other than checking out videobay.
But the reasons for it, is already described by you. Removing proprietary apps for normal browsing. Sure, the recent flash may use less resources using hardware acceleration in latest releases, but also brought some instability with it. Not sure why you brought up banners not taking up much resources, when we were discussing about YouTube. Well, flash does take up a lot of resources, especially having multiple pages open. If you use tabs, you'll likely have multiple pages open at once...and that may kill that netbook.
I'm for open source, even if it initially isn't as good. Knowing that will change down the road with more aids and tools than before. It's just not two OSes that we should worry about.