I used to buy all my ebooks from Fictionwise. I loved that they offered multiple formats, and if you changed up your reading device you could just go to your Fictionwise library and download the same book in the format you needed. I also loved the fact that most of the books I wanted were DRM-free.
On a totally selfish note, my ratings on FW tended to be higher I *think* because the genres were so wide and varied that there wasn't as big an expectation of "traditional romance" from readers. Hell, I bought my very first straight up erotic e-book from FW. It was Captain Hook/Tinkerbell and it was incredibly weird. But wonderful.
When B&N shut it down, I was heartbroken. My friends? Not so much. Apparently they hadn't been buying there for a while.
So now I float from retailer to retailer. All Romance Ebooks is good for M/M and other romantic stories. I dislike the fact that you're stuck with the first format you choose, though. Their Omnilit branch is one tab away and holds their "mainstream" collection, but I haven't tried that yet. I don't buy from Amazon if I can help it. I have a Nook, so shopping should be super convenient but I sideload most of my books through Calibre so not so much. I do tend to get a lot of graphic novels through the Nook store which worries me since I feel like the demise of the format I'm buying them in is inevitable. Sometimes I buy direct from publishers, and a lot of them have varied formats plus offer different loyalty programs. If the publisher is new or sketchy, though, I don't like to give them my credit card info. In those cases I go to a third party retailer for sure.
Fictionwise shut down a while ago, but I started thinking about it again when a reader emailed me asking if more of my books would be uploaded to Kobo soon. This is my trade and I should have been familiar, but sadly I didn't even know Kobo was a thing. After going to the site it was pretty easy to see that LSB and Torquere uploaded books to Kobo, but my other publishers did not, so unfortunately I had to tell her that I didn't know whether my other books would be uploaded there. I do intend to ask about it, though, since I know how it feels when your preferred retailer doesn't carry what you want. And, yeah, it had me really missing Fictionwise again.
So help me out. Where do you buy your e-books? Why do you like to purchase them from there?