The 7-inch size was what got my attention. I had a look at the iPad when it first came out, and the first impression I got was of a device that was too big, clumsy and fragile to carry around. The Playbook is easy to handle and fits in a coat pocket, or easily in a small tote bag. I can see it might not appeal to everybody, but it really works for me.
The 7" form factor is the only thing that made me buy it, I had an iPad before which simply didn't get enough use because I felt it was an inconvenient size. If I felt there was a viable Android alternative which was also 7" I definitely wouldn't be here right now (Possibly MediaPad?), but for the moment it will do.
if i wanted a 10 inch, i would have gotten an ipad. The portability of the playbook is what appealed to me. I want to browse and take pics and videos and show them to people as i have an online business. Carry the ipad or xoom and you will hate it. It is so freaking big, is like carrying a handbag everywhere you go. I simply put it in my pocket. I take it everywhere and do what i have to do with it. Hold the ipad or xoom for 30 minutes and you will feel the weight and want to drop them quickly. Not with the playbook.
I have both the ipad and the playboolk and like the pb form factor better than the ipad... The ipad is big a bit too big for me. I was waiting for the hp touchgo but the thing never came out!! :-(