The Primer supports Epub, PDF, html, Mobi, FB2, and txt for ebook formats, and according to the specs page it also plays MP3, WMA, APE, FLAC, AAC, RMVB, VOB, DAT, MP4, FLV, and 3GP. I do not have most of those formats so I can't test it. I got around 10 hours of battery life before I had to recharge. That's not bad for a LCD based ereader.
I like the general feel of the Primer. I kept setting aside the Literati so I could instead read on the Primer. It's not the prettiest ereader on the market, but using it was pleasant. It doesn't have any features beyond bookmarks and page jump, but I don't see why that would be a problem.
I found one rather curious feature. According to the CPU maker (they developed the firmware), the Primer does not support DRM. They were quite certain that they did not add this feature. However, there's a problem with that. My review unit worked just fine with Adobe DE. I've authorized the Primer and transferred several DRMed ebooks on to it and they work.
I'm fairly certain that it's not using Adobe Reader Mobile (the reading app on Sony, Nook, etc), though. An ebook will look about the same whether you read it on NookStudy, Nook4PC, or Sony Reader Library. The Primer is showing a several major differences in how it displays ebooks. Add that to the fact that I've messed with my laptop a lot (my Adobe DE install might not be kosher anymore) and the fact that Skytex aren't seeing this feature. I don't know if you'll have this feature, so don't count on it.
I wanted to include a special note about the video becuase it was a lot better than I expected. I'm not a video buff, but I think one might like the Primer. It came with several clips, and they played at full screen resolution (800x480). (I double checked on my laptop.) That was impressive considering the CPU was only listed as 400MHz. 16GB cards aren't that expensive now and it's enough for quite a bit.
I really liked this device as a $99 ereader, and it really does have a good reading experience. But I've been told that the retail is now $129, and that's just a little too much. TBH, even at the original price it had a lot of competition.