I just got my Timbuk2 sleeve to fit my iBook (12") yesterday and, boy, am I pleased! As much as I like the Bag-Builder on the site, I felt a little apprehensive before the sleeve arrived as they don't have the best photographs of their products (although there are plenty of well detailed drawings and written descriptions).
Anyway, this is a seriously gorgeouos sleeve that fits the iBook perfectly: it is a little snug but I know that it will loosen a touch as it ages. I opted for the navy waxed canvas which is gorgeous although I think I could have opted for a less conservative colour
The padding/protection is very sturdy and thick (ain't nothin' gonna hurt my baby now!), the handle is comfortable, and the latch looks smart and will prevent the iBook from slipping out--although I can't see that happening! All in all, I think this is a gorgeous product and it just firms my conviction to buy one of their other bags some day down the road that can also hold my sleeve. I just wished I could visit San Fransisco to see the rest of their products