I've got the 350 and 950 as well as the Kindle WiFi (K3). I like the 350 for its portability. It will fit into my shirt front pockets when I go places. I like the 950 for sitting at home reading with its bigger widescreen that works great in landscape mode with two columns. But I hate the Sony PC software (Sony Reader Library) and the Sony website for buying books.

I like the K3 for its simplicity and reliability and the fact that I can read MOBI without converting, tho converting is fairly easy. The K3 is a bit better for the PDFs I read and the Amazon Kindle book website is way better than Sony's.

I had an Aluratek Libre. Yes it has so-called support for many formats, at least non-DRMed formats. But two things were a turn off. It had a crappy LCD monchrome screen that looked metallic in certain lighting and had very low resolution. And most of the formats were presented like a text file with absolutely no formatting. The Sonys and the Kindles can view text files too, so no big advantage for the Aluratek. It should have to use true formatting to claim those formats!