Pros: Small, looks nice, cheap
Cons: Slightly bright/lean sounding, can be noisy
Fairly neutral but sounds slightly bright and lean sounding at times. To my ears, definitely more so than the O2.
I had them both within the last 6 months.
I felt it sounded good with the HD-650, HD-598 and my DJ100 but just decent with my Q701. For my Q701 with this amp I would probably prefer to use it with a warmer sounding source such as the Fiio E17. I think the docked Ipod Touch 2G to Magni made the Q701 sound a bit harsh/tinny/metallic sounding. Modi to Magni was a little better.
I sold the Magni after a few months and switched to the O2. It's slightly better but it does cost a little more. I think the O2 is a better match for brighter headphones, but still not perfect.
For very bright headphones the E9 sounds pretty good. It's much darker sounding in comparison and has some warmth but it's not transparent.
BTW my favorite budget setup would be O2 + Modi.