I ♥ 8.5x11. It's standard, Easy to print at home, and easy to handle and set on a shelf.
My only frustration is knowing the actual measurements of a 8.5x11 scrap album since they aren't really that size but often closer to 11 3/4 x 12 or even 13. Some brands list this but others (We R Memory Keepers I'm talking to you don't. It's frustrating because I need them to fit on the shelves.
I use 8-1/2x11 for my BOM, and (other than 12x12) I use 8x8 -- especially for a recipe book I'm putting together. 6x6 was just too small to be able to read the recipes and 12x12 would take up my whole counter!
And get the 3-ring binders! They hold WAAAAY more than the postbound albums do.