Fallout 3 was all Bethesda. It was just New Vegas that was done by another developer. So yes, there are things they should have learned from Fallout (3). But seeing how I don't have a console version of Skyrim to compare, I can't say much about their improvement.
The PC version runs almost flawlessly for me. I've had maybe 3 or 4 game crashes on my way to level 50, and patches have fixed most all my little issues already. There are still occasional annoyances, like standing over the corpse of a bandit leader that a quest still needs you to kill, but a quick console code respawn works as well as a patch in those cases.
I've found that with enchanting you can get 200% magicka cost reduction in whatever combination of spell schools on a single set of gear (body, head, ring, and necklace I believe). I went with half of that and my rogue can now cast all illusion spells for no cost.
I'm still loving this game so much that I haven't even launched Zelda yet.