For mobi reading, I use the Kindle app.
For DRM-free epub, coolreader 3.
I tried aldiko 2.x but reverted to 1.x which doesn't need to be faked out. I use it mostly as an organizer and to access OPDS catalogs online, while waiting for Coolreader and/or to debug/improve their OPDS support. When that happens, I'll be done with Aldiko. Its not bad, I just prefer Coolreader. I really like the dual column landscape and how it handles multi-level TOCs.
For Library access and ADEPT drm'ed epub, I keep Overdrive.
For pdf access I keep repligo.
I keep Nook handy in case I ever want a book that Amazon doesn't carry. Hasn't happened yet, but theoretically...

I tried Kobo but saw no reason to keep it.
I'm waiting to see what Bluefire for android looks like but for now Coolreader 3.45-11 is my reader of choice.