One thing is for sure, Jessica Alba uses this phone at least for a month and when she was at the WP8 presentation, she did not seem to struggle while having the phone in her hand. And she was holding it single handed!!
I can imagine it being a bit inconvenient if you are talking using this phone for more than 10 minutes (and not using headphones), or in your pant's pocket, but oh well. The phone is solid and that is why I think this is the first smartphone I will have, that I will not buy a cover for.