I have two SP1s I use for overheads on drums. For $35 each, I like them in that application. Of course, the world of microphones is your oyster and I'm sure many here probably dismiss these in favor of far better and more expensive mics.
Let us discuss for a moment "you get what you pay for," and "the law of diminishing returns" shall we? Yes, let's shall, but let's do it in ghetto context.
The MCA SP1 is as good a mic as any under $80. At the $80 level, you can get a Studio Projects B1, which is as good a mic as you can get for $150 or so. From there the playing field opens up. In ghetto terms, a SP1 is your best bet until you can afford a SP B1. That's not to say there aren't good used mics, dynamic or condenser, for under $80, because there certainly are. Are they better at $40? Depends on what it is and for that you need to know what you're looking for. Once you know what you are looking for you start edging towards "Ghetto Pro", meaning you know how to maximize a severely limited budget.
Assuming you don't know what you're looking for, then in general terms a MCA SP1 is a safe bet for the price, at least as far as I'm concerned, as long as it's $40 or under. Depends on the application. It's not a great vocal mic in general, but it's better than the MXL 990. It's probably better than any ghetto-budget dynamic (although some would argue a Shure SM-57 is ghetto-style and makes a good vocal mic). It's pretty good on guitar amps, relatively speaking (that is to say: in a ghetto sense).
The main question is, if you can find a Oktava MK219 for nearly the same price (ghetto-wise that means within $5 or $6), you may have to make a choice. The Oktava is dark and has issues, but it does have more character. Do you want a character mic? Later on, when you get to be "Ghetto Pro" the MK219 is supposed to make a great snare mic although I can't attest to that. The SP1, as I said, works well in pairs as drum overheads and on amps, at least for me.
But, if you are ghetto-styling, need just a mic for now, need a mic specifically for vocals and can spare the extra $30-$40 I would advise a SP B1 over the SP1. But, if not, the SP1 won't disappoint you.