i've been using pocket pages in my scrapbooking since around 2008. Back then the only ones you could get were 12x12 with 6 slots for 6x4 photos made my American Crafts. i still use that size sometimes. i used them in my travel album to include additional photos, journalling and memorabilia and they'd sit next to a 12x12 layout.
i still do that today, only now there are many more size options (thanks Becky Higgins!). I usually plump for something like the Project life Design A or Design H.This is because the most common size photo i have printed are 6x4 and i have an abundance of 3x4 cards to use up. i love using these to enable me to tell more of the story. It also means i don't have to worry so much about fitting my journaling into the design of the page they'll sit next to and that makes putting a page together much easier for me and more fun! The size of pocket page i use is determined by the amount of additional stuff i want to include.
Pockets are also great for housing memorabilia like tickets, as i did on this page about the London Olympics.
i can see myself using pocket pages more regularly because i am in that season of life where a lot of my friends are getting married and i have many beautiful wedding photos to scrap. There are some stories that i want to tell from those events of course, but the photos which don't really have a story but which are too beautiful to sit on my hard drive can be slipped into the photo pockets. With some pretty papers and embellishments too of course!
Are you using pocket pages in your regular albums? i'll be back on Thursday with some tips.