i think it really depends on where you are going to be looking and "purchasing" content.
If you like the Amazon shopping experience. I have a Kindle DX and a 1st Gen kindle with a broken screen.(Any ideas what I should do with it?)
My wife has a Sony PRS 505. Its a pain finding the books you want to read for the sony and a hassle sometimes to convert. But she has that book cover with a light integrated into it so I would have to pry that from her cold dead hands.
The DX is nice but I don't really have a lot of books with Pictures/ PDF, so its basically a giant screen, with 3G.
I have started carrying the Astak more lately, It fits into a cargo pocket. And well I don't have to convert much. I like the File format vs the Kindle/Sony.
But there is really no converting with the Kindle, since 99.999% of your content is coming direct from Amazon.
With the Astak you have to get "creative" at times where you find your books you want to read.
My advice look into a Pocketbook 360, looks good, pretty open with file formats, not sure if it reads as many as the PocketPro, Can any one Clarify that for me?
But yeah well I dont know...