Hear me out before you draw and quarter me with a rusty Merkur blade.
I shaved for 4 years exclusively with Merkurs. Hey they came with my Futur and were the same brand, so what could be better right? I ordered everything from Classic Shaving and that's all they had. Ok they had Feathers, but they cost a buck more. Nobody else does this old-timey safety razor thing anyway so that must be all there is anyway, right?
Ahhhh....(angelic sound) I found B&B
I learned Merkurs suck. I bought Derby's, Crystals, 7 O'clock, and what I settled on, Feathers. My shaves got much more consistent, and better.
After all that, I still can't bring myself to bad-mouth Merkur blades. Yeah they aren't the best, and they are over-priced, but I was able to get shaves that kicked M3 in the butt for over four years with them. At $5 for 10 they were still much cheaper than M3s.
So in the end Merkurs may not be very good compared to other blades, but I wouldn't be here without them.