I main MK, and I think he has good specials! I find myself using them often, mising up combat and racking up damage! Different strokes for different folks I guess, but I think they are mostly really good and useful in his overall strategy. Well, here I am to give my "expert" XD opinion on Meta Knight's specials:
B, my favorite, Mach Tornado! Great for damage. I wouldn't spam it, but I would use it alot and throw it at people when they don't expect it. Keep tapping that B button, extend the duration and lift opponents off the ground! As mentioned, will block some small projectiles. Works great on a lone enemy, also good fro crowd control in free-for-alls. I use this one a lot, it works well!
Up B, Shuttle Loop! A viable kill move, just be careful. If you use it near the edge or you are not used to gliding, you may SD. Can hit enemies on platforms above you, sometrimes hits twice. Try to sweetspot it (initial trajectory is like Marth's Dolphin Slash). Use when unexpected, pretty good for getting Smash Balls above you. Try to use the Glide Attack to for more damage.
As for Side B, I don't fin myself using Drill Rush too often. I usually use it on accident. Good for catching opponents offguard or recovery, but thats about it. No high damage, can be punished if you miss. Careful, use in moderation, but don't neglect it! Good in Free-for-alls. Use a Dimensional Cape to get out of a huge mass of fighters, and plow through em with Drill Rush (also works well, if not better IMO, with Mach Tornado).
His Dimensional Cape, Down B, is interesting. The after-attack is strong and a good KOer, but if you miss with that sword slash there is an eternity of lag by MK standards. I use it for mindgaming and getting out of sticky situations fast. Adds significantly to Meta Knight's nimbleness and maneuvarability, he can pop up anywhere, keeping foes on their toes. A good move nonetheless.
Dount anything I've said hasn't been siad before, but I'm an Meta Knight main, and I'm pretty good, so I thought I'd share my views on his specials!