My first MIDI sequencer was a Roland MSQ-100. The user interface of that thing definitely left a lot to be desired. But back in those days, I was willing to jump through pretty much any hoops to do sequencing.
Later on, I had a Roland MV-30. I loved the MV-30's sequencer, with the recordable sliders for things like pan position and volume.
Never heard of the MV-30 until now. It looks like a pretty nifty box. I have an MV-8000 and I think the sequencer is the most straight forward thing on it, surprisingly. And, like the MV-30, the sliders are really useful for doing MIDI mixing.
The size of the screen makes a big difference to the ease of use. I had it running CC's duties before I got sick of turning it on and waiting forever for it to load it's OS just to use the sequencer. It has some great composition tools as well, like a crescendo programmer and sweep generator. The sampler is pretty bloody good too, but after owning an E-MU Ultra, everything else feels hobbled.
* markd Waits with baited breath for the MPC-X
I have a love/hate relationship with Roland. I love their work in the early days, they helped make synths affordable to the average musician. Now they have sort of become obsessed with chasing the missed money their synths from 80's are making on the 2nd hand market.
In my mind, the R-70 was the pinnacle of their drum machines. Not the R8 (or the 808 or the 909). I've got an R8 and it's a tragic 80's studio drums module with a sequencer. Even with the cards it still sucks. Nothing like the R-70 to program and crappy rompler synthesis which may as well be a DR550. In fact, I'd swap the R8 for a DR550 if the thing didn't shit the bed while it sat in a cupboard for 5yrs (powers-up to a garbled display and no sound, not the battery I tried that and decided it sucks anyway so back into the cupboard). At least the DR550mkii has 808 samples on board. And the only reason I'm singing the praises of the R-70 is because since the Pyramid, I've decided I don't need to chase one any more.