I have a BDP-HD1 pre-ordered from Tweeter and also already have a Sony BDP-S1 I got from Best Buy, which with their holiday return policy, I have until 1/24/07 to return if I decide I don't want to keep it.
Since I have a Pioneer Elite PRO-FHD1 plasma and a Pioneer Elite VSX-84 TXSi receiver, I'm already biased in favor of going with the Pioneer BDP-HD1. However, if I do, it won't be because of freeze-ups or other such problems with the Sony since I have not had any with it. For those having such problems, one easy thing to try is to make sure the disc is clean, even if it just came out of its case for the first time. I learned this with my Toshiba HD-A1 and HD-DVD's, and it has certainly saved me some problems. It may not be a cure-all for the Sony, but may be worth a try.
Not saying there are or are not real problems with the Sony, just that not everyone is having them.