I use Audeze LCD-2 Classic (w/ Dekoni Elite velour pads), Focal Clear, HiFiMan HE500 (w/ ZMF Ori lambskin pads), Sennheiser HD650, HD800, and ZMF Auteur as my main headphones for music.
For gaming, I've been a heavy user of AKG Q701, Audio-Technica ATH-AD700X, Beyerdynamic DT990 (600 ohms), Philips Fidelio X2, Sennheiser HD700, Sennheiser HD800 and Superlux HD668B (w/ Brainwavz velour pads).
For under $100, the M220 sound great for soul, blues, jazz, classical, folk and soft rock music. They're fairly clear and detailed with decently natural timbre and a spacious soundstage. While the bass is fast, tight and punchy, it rolls off already at the mid-bass. There's no oomph and nearly no rumble. I don't recommend these headphones for electronic, hip hop or rap. I thought they were good for hard rock and heavy metal, but the mid-bass was muted and the treble tended to sound too crunchy.
For online/competitive shooters, the M220 are for good for hearing and locating footsteps and other sound cues.
To complement the M220, I recommend getting Monoprice Modern Retro for $25.
I replaced the pads with Beyerdynamic DT770 pads which are deeper, softer, silky smooth, breathable, and of much higher quality. I replaced the cable with a generic one for $12 on eBay. Low20101020 is a reputable seller there and I recommend them.
The rest of the build quality is fair for the price. It's mostly made of plastic, with the housing made of metal. It's very lightweight and fairly durable. It doesn't rattle and has no squeaky parts. It has a nice finish all around.
The cups tilt and swivel, so they should adjust to anyone's head. The strap has great weight/pressure distribution and doesn't create hotspots on top of my head. The self-adjusting system works perfectly for me, the headphones don't rest on my ears and they don't push my ears upward. The clamping force isn't loose or too tight. I have an average sized head and average sized ears.
I liked the M220 so much that I bought them in white (can be found on Amazon) because they look beautiful with the silver-gray DT770 pads. I like keeping a collection of budget gems, like these along with Creative Aurvana Live!, Koss Porta Pro, Koss KSC75, Philips SHP9500, Monoprice Modern Retro, Sivga SV007, Superlux HD668B and HD681 EVO.
For gaming, I recommend getting a 3-pin mini XLR to TRS 3.5 mm adapter from mimic-cables.com to turn them into a headset with V-MODA BoomPro.
Would recommend to a friend.