Sound — 9
My rig is a Fender strat into a Vox AC15. I use my M9 for all my delays, reverbs, modulations, filters, and looping. The delays sound great, and there are enough to capture almost any tone you're looking for. The modulations are great too, featuring phaser, flanger, chorus, tremolo, vibe, and Leslie tones. Some of the distortion models are very nice, but aren't excellent. The distortion models are the weak area of the M9. Filters sound great, I use the Voice Box model to play Sonic Youth's "The Diamond Sea". The M9 definitely excels at delays, reverbs, modulations and filters. The Compressor models are also very nice, but the dirt models aren't the best. IMO, it's ideal to use your favorite analog dirt stompboxes alongside the M9 if you can, it'll give you the best tones all round.
Overall Impression — 9
I play lot's of different genres of music, and the M9's versatility is a perfect match for my eclectic taste. I can go from gritty blues rock to swirling shoegaze to stripped-down Indie to atmospheric post-rock in half an hour, and the M9 can handle it all. I've had the M9 for about 4 months now, and it's definitely become an irreplaceable part of my set up. I rely on it for quite a bit of my sound, basically anything that isn't just completely clean or fuzz. I love that it's incredibly versatile, easy to use, and has so many effects available.
Reliability & Durability — 9
The M9 is built extremely well, I'm sure I can depend on it for a very long time. It's in a nice metal enclosure that could definitely survive getting beat up on the road. The screen is small, thereby having a better chance of survival. It also seems pretty tough. I would definitely gig the M9 without a backup. In fact, I'd have no qualms about only taking my M9 to a gig. Not only could it handle all the tones I'd need, I have no worries it could survive.
Ease of Use — 9
Although the M9 is a multi-effects unit, it is very intuitive to use, and is designed to act more like a pedalboard than your regular multi-fx unit. It has 6 'scenes' which are like 6 separate pedalboards containing 6 pedals of your choosing. The looper is also very intuitive. Surprisingly, there's very little tap-dancing involved, unless you're doing lots of looping and scene-switching. Editing patches is very easy, you just have to turn the knobs located below the screen. The effect 'types' are colour-coded to let you know at a glance what kind of effect each is. The manuals are very helpful. One explains general functionality, and is more like the regular owner's manual. Then, there's a separate booklet that helps explains each effect, and it's unique characteristics.