The Optimiser system is really quite simple. It's a torsion bar (or spring-steel if you prefer) which is loaded by a cam on the tang of the closed blade. The torsion bar tension holds the blade closed as well. The load springs and is released when the blade pivots aprox. 30°, passing the apex of the cam surface. The load "throws" the blade the rest of the way to its' full-open position, where it is locked in place by the liner-lock and the torsion bar sits completely relaxed. You can feel where the cam re-engages the torsion bar upon closing. I'd say it's around 90° from the open position.
On the Apparition, you can remove the torsion bar and make it a manual folder if you like. I haven't tried that with mine yet, and may never, because I bought it for the A/O feature.
Yes, you defintely can get one for under $100. I paid $89.95 for mine about a month ago from an eBay dealer. Brand new in box and the guy shipped it faster than I knew was possible, charging only $5.50 for shipping. That was the best deal I found on eBay at that time, but I've seen close to the same deal several times since then just surfing around in there.
The 670 came out of the box with a very sharp blade. The only thing I've done to it at all is draw a few strokes on my ceramic "V" sticks. I would think that you really shouldn't have to "sharpen" it per se, unless you have a specific need for it to be sharper than arm-shaving-sharp. Maybe just touch it up a bit with a steel or ceramic sticks, or maybe a strop.
That said, if I had the money I would buy an EdgePro system. They come in three or four configurations, from basic home-use to professional-grade, and range from $120 to close to $200. Since I didn't have the money when I bought my sharpening kit though, I went with a GATCO Diamond kit. I got it from one of the internet knife dealers for under $70 bucks including shipping. Just Google GATCO or Lansky or EdgePro and shop around. You'll find the best deals if you just keep on looking.
Hope that helps, and good luck with your new Apparition. For my tastes/purposes, it's an awesome knife.
Blues
