Amazon has the Kindle, Barnes & Noble has the Nook, but Borders has opted to offer a range of dedicated e-readers. There's the Kobo eReader for $149, the Libre eBook Reader for a very affordable $119 (though do note it's an LCD display, not E Ink, and its available only for pre-order as of today), and the Sony Touch ($169) and Pocket ($149). The Kobo seems to be the 'flagship' model and Borders is throwing in a $20 Borders Gift card and "Double Borders Bucks" if you buy now. So for effectively $129 you get an E Ink e-reader, though you'll have to sync books onto it via a USB cable; there's no wireless connectivity.
The Borders e-book store is also rolling out with broad support of non-dedicated devices; they have e-reader software available for iPhone, iPad, Android (2.0 and later) and Blackberry, as well as PC and Mac computers. These all do support wireless downloading of e-books, but don't have the syncing features of Amazon's Kindle and Apple's iBooks ecosystems. If you only read your books on one device that won't matter, but for those of us who jump back and forth from mobile device to...uh, slightly less mobile device, that syncing feature is a nice perk.
Border's e-reader apps let you purchase books from within the e-reader software; that seems to be an important differentiator to some, though I personally don't see dumping out to a browser to buy an e-book that much of an inconvenience. I tried the iPad and Android versions of the e-reader software and surprisingly found the Android version had a better store experience. The Android version has a row of icons at the bottom of the screen that quickly take you to a "Discover" section (with lists such as New York Time's Fiction Bestsellers, Oprah's Book Club and 2010 Pulitzer Winners), a Browse section that lets you drill down through categories and subcategories (e.g. Sci Fi & Fantasy -> Fantasy -> Historical and finally a list of titles), and finally a search box. The iPad version of the store offered a few lists on the front page. When I last checked they were Just Released, Today's Top 50 and then a couple of semi-random lists: e.g The Thrill of the Chaste (religious fiction) and Just For Kicks (soccer; at least I understand why that was there). The category browse is there via an otherwise unlabeled Jump To button which leads to a choice of even more lists or the category drill-down.
The actual reading experience on the iPad is good, with a choice of 4 fonts and a good selection of font sizes, a variety of page-turn animations (including 'None'), a brightness slider and a night reading mode. There's no option to change the page color. There's a progress meter that shows at a glance roughly how far through the current chapter, and the whole book, you are. The Android software offers 3 fonts, 5 font sizes and a day/night toggle. It shows the page number of the chapter and how far you are into the book in terms of percentage.
If there's a way to bring non-Borders content into these apps, I haven't found it yet.
Of course, if you're not using a dedicated e-reader you have choices beyond Borders. The iPad supports iBooks, Kindle, Barnes & Noble and now Borders e-book shops. Android supports Kindle and Borders. The Blackberry supports Kindle, Barnes & Noble and Borders. And so on. The common theme here is that Kindle runs on everything the other bookstores run on, apart from the dedicated e-readers. So why would you choose the Borders e-book store over one of the others? Honestly I don't know. Borders does have a list called "Can't Get These in iBooks" which just seems like an attempt to try to sell themselves as the best e-book store on the iPad and iPhone, while blithely ignoring the elephant in the room that is the Kindle store.
Comparing pricing across these stores is hit or miss. You can check a lot of books and find all the e-book stores have them for about the same price, then stumble upon an anomaly like Stephen King's Under the Dome which is $9.99 in the Kindle store, $9.99 in the Barnes and Noble store, $16.99 in the iBooks store and $16.99 in the Border's store. On the other hand, looking at a random new release, Sizzling Sixteen, it's $12.99 across all the stores. And I'm sure if you dug around enough you could find books that are cheaper on iBooks and Borders than they are in the Kindle and Barnes & Noble stores. In the end what I do is install all the e-reader software apps, then compare prices when I'm ready to buy a book and buy it from wherever is cheapest. If they're all the same price, I personally go with Kindle since it syncs bookmarks and last read page between my iPad and Android.
And if you're using a dedicated e-reader, then you just have to buy from the store that your device supports, which is the number one reason I've avoided, and will continue to avoid, dedicated e-reader hardware. [Update: See the comments, I may be wrong about this, and I'd welcome more clarification on how various e-readers interact with the different stores.]
Border's is the last major bookseller in the US to get their e-book house in order. Are they too late to carve out a niche? Possibly. It'll depend on whether they can cut better deals and offer e-books at better prices than the other stores. Or failing that, sell a ton of Kobo e-readers to customers at their brick & mortar stores. To their credit, they've already got better hardware support than Barnes & Noble does (B&N has yet to release an Android app), and it'd be nice to see them get cross-device syncing working. But at the end of the day, it's all about having the widest variety of books available at competitive prices. Does Borders have more clout than Amazon when it comes to negotiating with book publishers?