First of all, a misconception: Upstart isn't about parallel boot. (This is from discussing a lot with the Upstart author at LPC)
Second: Parallel boot is the wrong technology. It's a good answer to the "I want to boot faster" question, but it's absolutely the wrong answer to the "I want to boot fast" question. Eg it's something that gets you from 45 seconds to 43 seconds.... but not to 5. (note that Fedora 9 already uses Upstart.. and still boots in 45 seconds).
Parallel boot is the wrong thing; it ends up meaning that you're not really doing the critical path in sequential order; but let the system get distracted from that.
Asynchronous boot (where you let the critical path go sequential, and non-critical pieces asynchronous) is the right answer; the article has a graph about this. And Asynchronous boot you can do just fine with SysVinit.... no magic about that.