I bought one of these Roland D2 'grooveboxes" back in 2002....it was really exciting and i have used it ever since as a sequencer, and drum machine....the realtime control of the 'D-field' controller was what hooked me in the store where i bought it. was able to instantly apply manipulations to the pattern, things like playing the pattern in reverse, or emulating turntable tricks are simply addicting.
Combining a synthesizer like this with a guitar and effects can transform someone into a solid 'one-man-band' in no time. Well, truthfully, it did take sometime to perfect my performance...without lots of practice programming midi patterns, and editing tones any device like this would not show it's true potential.
There are pre-set patterns, but it is truly made for programming original patterns, in realtime, and rolands 'step' programming methods...in the 'step' method you can do some precise editing with the midi sequence...I personally prefer the realtime method, and on a 'instant gratification' scale, it rates a "10".

Here is the description of the Roland D2 which i copy&pasted from 'vintage synth explorer':
Roland's D2 Groovebox is a compact, performance-oriented Groovebox (sequencer/sound module)--sort of a smaller MC-505--designed entirely around Roland's D-Field Controller technology. This touch-sensitive pad makes it easy to program and modify patterns, sounds, effects and more simply by touching the surface. It has all of the 505's sounds and a similar sequencer with 150 all-new patterns including the latest 2-Step and R&B styles.

The D-Field controller at the heart of the D2 (also featured on the V-Synth) offers three distinct modes: SOUND makes playing patterns and sound effects easy by touching the D-Field; XY provides simultaneous control over two parameters (e.g. filter cutoff + resonance); SPIN creates turntable-style effects by tracing the pad in a circular motion.

The D2 has more than enough sounds inside, with 600 Preset patches and 30 Preset drum kits from the MC-505. These dance-oriented sounds include ultra-fat bass and lead synths, screaming TB-303's, dance piano and strings, plus 30 floor-pounding drum kits. Phrase/Groove loops are also plentiful with 150 patterns plus 240 RPS (Realtime Phrase Sequence) patterns. There is a new Step Recording method using the D-Field and 32 LEDs as well. Separate Reverb, Delay and Multi-FX sections with Groove-oriented algorithms add space and effects to your sounds & grooves. And with the D2's Megamix function, it's easy to remix patterns into your own creations using the D-Field or Value dial.

Today i also have the Roland MC-909, which is a monster of a 'box', combining sampling, synthesizer & 16 track midi sequencer with a boatload of studio grade multi-FX....I also use the Roland MKS-7 Super Quartet, an Analogue Midi Synth Module circa.1985, and the three of my Roland's are perfect for whatever sonic experiment i attempt.