I got one used during the production lull and love it.
The big surprise for me is the 6-track recorder. I can record inputs, outputs, whatever I want. I was using the Bitbox for that, but this is more flexible and lets me free up the Bitbox for what it does best (one shots). I can simultaneously record an input and multiple effect chain variations. It's nuts.
I sold my Nord Drum 2 after getting the Bitbox, as the Bitbox has more sample slots and is totally integrated with my modular (yes, the ND2 does synthesis, but it's so fiddly that it made more sense to make the sounds on my computer and just load them onto the SD card). I'm also considering selling the Folktek Matter, as it is starting to feel like a preset box with a fiddly interface. I feel like for traditional one-shots, the Bitbox is a good stopping point. The only thing on that design that I would want is more modulation.
The ER-301 is a different beast to me. I sold off my Dervish (multi-FX processor), Echophon, and a few others (Probably the O'Tool soon). The sampler is amazing, but the eye opener has been just how damn good it is for being the center of the system. It has 16 DC-coupled full-range and high sampling rate inputs, four gate inputs, and 4 AC-coupled outputs. So far, I've built wild pitch-shifting delay patches (where the pitch-shifting can happen either in the delay or by manipulating some samples), multi voice additive synths, and more. I've used it as a mixer, an FX box, a generator, a recorder, sometimes a few of those things simultaneously.
I'm thinking of building a matrix mixer and keeping that as a quicksave slot (on the forum, he announced he's quadrupling that quicksave slots from 6 to 24). I have some sampler patches on a quicksave, along with some crazy additive stuff.
I can't wait for the SDK. I'll definitely write some stuff for it once that's available (unless it absolutely requires Assembly >_<)