E-Readers?

There are frequent posts out there on the merits of e-readers in general. I have one and love it (I went with the Kobo). That's not what this post is. What this post is about is the particulars of the different E-readers on the market.

I can talk up the Kobo well enough, but I can't answer most of the questions I get about the other e-readers: the Sony, the Kindle, the Nook etc. For example, I've heard from some people that the Barnes & Noble E-reader has the ability to do colour.

One of the other key questions concerns battery life. The Kobo typically lets me read between four and six books (full novels) before I have to recharge the battery. And the charging time is about three to four hours. So, what is it for the other major e-readers out there?

And formats? I've heard that the Kindle is restricted to buying books from Amazon only. But I think I've seen hints that there may be books for the Kindle elsewhere. Which also lets out the ability to use the library e-book system. But what about the Sony and the Nook? I know the Kobo uses both the e-pub format and pdf. I've seen some hints that at least some of the Sony e-readers do too (they can use books bought at the Kobo store). But, I don't know for sure.

What to you are the advantages of the e-reader you chose? The ability to take notes? To do more than just read a book? I'd like to know. I went with the Kobo, partly because it was the first one I could afford and it was there. I'm glad of the choice I made, but I'd still like to know more about the other options out there (partly because it is a part of my job to try and sell the Kobo e-reader, and it would help me to be able to answer people's questions better).

Thanks. Your opinions are very welcome on this subject.