At the moment, it looks like the rewriteable (RE) disks are limited to 25 GB, the 50 GB disks are write once - at least according to [link|http://www.tapeonline.com/blu-ray.aspx|this] store. At $34.10 for 50 GB of write-once storage, it's not compelling to me at the moment - especially when one can get a 80 GB hard drive for [link|http://www.newegg.com/Product/Product.asp?Item=N82E16822144102|$42] or less, and especially since few other drives will be available to use the disks for a while (e.g. if the drive dies, where will you be able to read the info?).
Cheers,
Scott.
(Who thinks the format is interesting, but I'm not willing to pay early-adopter prices just yet.)