Kindle's advantage is also its biggest flaw - it only reads kindle format when it comes to DRMed materials. Amazon make it easy for Kindle users to buy from its stores, but Kindle doesn't support DRMed ebooks from any other sources. But.. still, there are plenty of non-DRMed ebooks out there, and they can be easily converted to the mobi format.
Sony's ebook reader has come a long way. Sony has made a lot of improvement to reduce screen glare and reflection for PRS650. Though I haven't got a chance to use one yet, from the reviews I've read, it's a winner. It does read standard DRMed ebooks (made with Adobe Digital Edition) from various vendors, if I'm not mistaken.
One thing though... I live in Singapore. I can't buy Kindle or Kindle ebooks from where I live. It's a country that Amazon will not sell their ebook products. Same with Sony. They don't sell their ebook readers here either. I feel I'm living in a backward country where nobody reads.
I probably need to buy one from unofficial, unauthorised sellers.