I have been buying and using the SP-2 pedals since I went to music school years ago. Used them on all kinds of shows and sessions over the years. I only recently gave up on them. There's much to like, but they have some real problems.
Pros: It's cheap and good for its price. Sturdy make. Has a polarity switch at the bottom - fits any professional keyboard. Yamaha, Roland, Korg, Nord, Kurzweil, etc,... either the sustain works right away, or one flip and it works good. Feels solid on the foot. Has a decent grip on the floor. If you're buying this pedal at this price you are most likely not worried about half-damper/soft controls etc., and you shouldn't. It does what you paid for it to do. Excellent for all kinds of contemporary music on the keyboards for live use, or in the studio with your keyboards or midi controllers. Again - it will work with any keyboard.
Cons: DURABILITY. For such a sturdy-looking design, it's really surprising how quick it stops working good. Now this may not be a problem if you are a hobbyist or you just intend for your pedal to sit in a corner in a house. But for touring keyboardists, or session players needing their gear to function 24/7/365, do beware. I went through 5-6 of these in about 2 years. Various times on stage my pedal would suddenly stop sustaining in between songs or sets. Or the polarity would get switched up. I keep spares in my rig just in case, but this happened so often it became genuinely annoying. For something that you literally use with your foot, it's borderline unacceptable that this thing can't be kicked around (gently) without breaking. It has got to the point that now when I play concerts where the backline company supplies the gear, if I see them handing out those pedals during soundcheck, I demand they change it. No joke. Also the pedal squeaks after a while. The squeak is usually at "I can ignore it" levels for live shows, but if you're in the studio it's a no-no. One time I had it hooked to a Nord Stage 88 EX for a recording session, and this pedal just couldn't stop squeaking. It sure didn't affect my piano tracks since I was going DI, but it did irritate the hell out of the vocalist - not a good look for me that day.
All in all, it's good for it's price. You get what you pay for. But if you need a professional, dependable pedal that won't die on you without notice, spend $10 more and get the Yamaha FC4A.