I see a lot of posts in this thread recommending that if I'm interested in 6x4.5 that I should just crop down from 6x6. I wonder to myself why that is. The advantage I see is less equipment to acquire.
That said, I've never been into cropping. I've shot digital for years and and very familiar with the crop tool in Photoshop - takes 2 seconds. Maybe it's just my eyes, but I've never looked through a viewfinder and thought, "I'll frame it like this now and crop it the way I want later." I prefer to "get what I see." Maybe I'm being naive or stubborn, but I shoot 6x6 because I like that aspect ratio. If I want to shoot 6x4.5, I would not feel comfortable shooting 6x6 with the mindset of framing for when I want to crop down to 6x4.5 later. I'm sure this is a self-limitation, but that's just how my mind works.