For various reasons (too lengthy to go into here) I will never buy a Sony reader (or Kindle) - personal choice.
But I am absolutely stoked that the best eBook format around -
FB2 - is being supported on Sony readers. That is outstanding! The lack of FB2 support is just one reason why I never bought Sony (or Kindle) - plus the general lack of other format support.
I see there has been a lot of support by Russian readers, not surprising as they are heavily into the FB2 format. If I had a Sony I would give this (and other FB2 solutions) a serious look. If you haven't tried FB2 it's worth a go.
All the best to the developers and users - enjoy!