I give a full voiced "meh" to the Speed King.
I have one on a vintage MIJ set just to have that vintage vibe. I don't hate it, but it certainly is it's own monster.
What I do like: The fact that it comes apart in two seperate pieces (very easy to transport), looks cool and just screams "classic", that it works smoothly (when cleaned and re-lubed-if older) and is certainly durable.
What I don't like: Very limited adjustability (spring tension and beater height and that's it!-it's hard to get a light feel on the SK), the "too far forward" design that someone else mentioned (I can only clamp it about halfway deep on the hoop; otherwise the linkage hits the head), and the "non-springy" feel. On most other pedals, assuming a middle of the road spring tension, when you take your foot off of it quickly, the pedal moves back and forth several times on it's own (even moreso on a chain and sprocket design, like DW or Camco). With the Speed King, you take your foot off, and it returns abruptly to its normal position and that's that, with no "springy" movements. Every Speed King I have ever seen or played does exactly that, no matter how it's adjusted.
I don't hate it, and I don't love it. As far as other direct drive pedals, I really like to use them. I play mostly heel down, and direct drive pedals are especially good for that. However, I own all sorts of pedals, chain drive, strap drive, direct drive and the SK. They are all functional and useable, and honestly I don't have a true preference. I can use pretty much anything. I've always believed that "its the player, not the pedal!".