I highly suggest anyone playing Blaster Master for the first time to look over the manual! (
http://www.vnoteschronicle.com/sites/default/files/games/blaster-master/graphics/blaster-master-manual.pdf) It's got a few maps of varying detail which will definitely help.
I remember trying this game as a kid and just being totally overwhelmed with the branching pathways and overall difficulty. Taking my first real attempt at it now, it's still very challenging at first. A few hours in, though, I'm really getting the hang of it and making significant progress with each new game. You really feel a sense of discovery when you finally come across the next boss or area.
The constant battle to keep your guy's gun powered up is a serious chore and a majour blight on this game. Visually, it looks unique with it's muted colour palette. Some of the backgrounds look great while others look strangely thrown together. The music is pretty great overall. Oh, and the slowdown? You can't really complain about that. It's a product of the hardware. Besides, it's an advantage when you're being swarmed!
Looking forward to hearing your thoughts on it!