The sound quality overall is pretty decent. Some of the algorithms DO stair-step, noticeably the Synth+Delay (I just turn the Resonance to max and let the filter pick out stepped sets of harmonics rather than trying to get wa-wa sweeps) and the LoFi (which is _supposed_ to sound bad, right?)
The much-vaunted ability to effect hi, mid, or lo, is kinda misunderstood. You can bandpass hi, mid, or lo frequencies, and then effect the narrower signal. You can't really effect, say, just the mids (though you could bandpass the mids and mix the effected signal with the original, but it's not the same thing.)
The Filter sounds good to me. Not quite as cozy-uppy as the one in my Yamsha CS-15, but good-sounding. The Flanger is quite usable. The Phaser is ear-twistingly great in headphones. Lo-fi is pretty useless to me, though it does get nice and ugly. The reverb is a throwaway: karaoke 'verb gone bad. The compressor is completely unusable: Not only is it a crappy-sounding compressor, but it's got that slight DSP delay on it, making one of my favorite compressor tricks impossible (send a mono submix of the drums to the comp, squish the shiz out of it, then blend with original for punch and focus.) without comb-filtering. Crap. The Voice Transformer emu is as picky (if not more) than the original orange-and-blue box, though I must admit that I've only used line in sources with it. The vocoder sounds surprisingly good, though you'll need to set up a custom mix to feed it with Carrier and Modulator hard-panned left and right. Not so great for live use. The drum machines are utter crap. Cheesy in a bad way. And this is coming from a guy who's used Casio SK-1 drums, UP Ultimate Percussion triggered disco-drums, and Sears-bought Yamaha cheese profitably. The hats are okay, and the kick in one kit is pretty happenin', but you're not going to make a beat with this.
The Synth (ah, the controversial Synth)... Well, it's not a 303. Good deal. The 303 is _tired_, people. It's Played Out. My buddy who worked at a used-gear store had a 303 for a while, but sold it, 'cos that lump o' circuitry was bo-o-oring. Good riddance. That said, the synf in the EF303 squelches like a good TB should, and actually sounds really really good. Eminently usable, but programming it via sliders is weird. It's pretty hard to differentiate between half-step increments on those little bitty sliding controls. Satisfying results, though. Much better than a Predictable-Piece-O'-Crap keyboard controller. Too bad no D-Beam for more sonic lysol, rubber punching bag weirdness and fuzzy control.
Negatives: just a global "Smooth on-off" control, rather than a choice of transition times. This'll make the steps sound late when you're sync'ed to external MIDI clock. No accent/envelope controls for the synth, and you can't use slide and rest simultaneously to do note fade-ins or -outs.
The FX that are good are quite good. The bad ones aren't even bad in a likable lofi kinda way. The coolness of the good 'uns outweighs the suck factor of the lamers, though.
Seems solid enough. I've got heavy hands (no DJ fingaz here), and it seems to be able to take it. I'd use it on a gig with no backup, though its usefulness for me is fully realized when looping and relooping nightmare glitch-mod sequences and resample-fests.
Basically, this is an effects box with 3 parameter knobs per effects program, any of which can be (one at a time) controlled by the step-sequencer.
The cool thing about it for me, though, is the fact that all of those 16 sliders transmit MIDI, making it a kick-ass controller for Ableton Live, my main composing environment.
The sounds are cool for weirdo glitchy progfreak stuff. I'm not so sure it'd be good with 4-on-the-boring-floor house music, though.