I've been on the lookout for one of these guys for a while. Unlike most of E-mu's Proteus-based ROMpler modules, the Morpheus doesn't usually turn up on the used market very much. I've been watching the occasional one appear on Ebay for a couple of years now, and they usually sold for around $400, which is about double what most of this era of E-mu modules goes for. However, recently several turned up on Ebay at once, and I was able to win this one at around $200.
Going back to the late '80s, when E-mu first started selling the Proteus modules, one of the big complaints about then was that they had no filters. When E-mu finally decided to rectify that, they didn't just implement software versions of the standard 2-pole and 4-pole filter types commonly found in analog synths. Instead of trying to re-create the analog domain, they took advantage of the software environment to create a huge variety of formant filters, comb filters, and some arbitrary filter equations probably never seen before (or since) in a musical instrument. Then, they gave each filter 2 or 3 variable parameters which can be tied to either the note value (which key is being played), velocity, or various MIDI Controllers. For example, one one filter type, the "morph" parameter controls the resonance; on another, it controls the number of notches in a comb curve.
Another feature that I was surprised to find, because I've never seen it commented on before and the older Proteus modules don't have it, is a very flexible and powerful universal event generator. It has eight steps, and for each step you can independently set time, slope, and shape (there are a huge number of linear, exponential, circular, and arbitrary shape choices). You can also set certain steps to be skipped or repeated based on certain events happening or not happening.
Like most of the Proteus-based modules, it has the notorious "peephole" user interface. You press a button to select a category of parameters to edit, press other buttons to move the cursor to a parameter name field. You turn the rotary encoder until the parameter you want appears. Then you press the cursor buttons to move the cursor to the parameter value, and turn the rotary encoder to change the value. I already have a Metro sequencer file with a bunch of virtual faders that are set up to send Proteus sysex sequences; I can edit most of the parameters on my Proteus/2 with it. Hopefully it won't be too much trouble to alter the sysex templates to edit the Morpheus parameters. There is a patch editor specifically for the Morpheus, called MorphEdit, but it's Windows only, and I'm running OSX.
And: the build quality of the Morpheus seems to be much better then the Proteus/2. The Morpheus' case is metal, unlike the plastic cases of the earlier Proteus modules. And the buttons and the rotary encoder feel better then the rather flimsy ones on the Proteus/2. It didn't come with a manual, but you can download manuals for nearly all E-mu products on their support page.