Notch didn't fix anything, I've ended up fixing my own damn Minecraft. Such a graphically simple game shouldn't kill my computer, but it did until very recently. Luckily I found out that storing the map file on a RAM disk partition greatly helps, and now I've finally got back into it. Before it was basically unplayable even on Tiny view distance, now I can have smooth lighting, detailed graphics and normal view distance (far if I feel like pushing it).
I have found out that Minecraft is a game that needs to be smooth to be enjoyable, but now that I can finally play again I have to say I'm quite impressed with some of the additions. The weather system, maps and trapdoors in particular are all great. I haven't actually come across any bugs, as of yet... (other than the crippling performance hit that has been around for months and I had to fix myself).