The "shift lever" brew arm for the Speedster is shown below, near the bottom of the photo.
It has three positions: Pump off (up as shown), Line pressure preinfusion (middle) and On (down). When the arm is held to the right of the "shift pattern", the barista can move between these three positions in one fluid motion; if the barista desires to maintain line pressure preinfusion without holding the arm down, the brew arm has a slot that can slide over the midpoint detent. The pump on position is maintained by moving the brew arm further down and to the left where its return is impeded by the midpoint detent.
Although the design of the brew arm could probably be less complicated, it fits nicely with the spirit of the Speedster's hands on, mechanical feel. Its location and the steam wand location do, however, favor those who are right handed.
As I mentioned earlier, the large water wand knob is non-functional; the water flow is actually controlled via the momentary switch directly below it. Above and to the left of the brew pressure gauge is the preinfusion valve piston. When the brew pathway pressurizes, a spring-loaded piston is forced outwards, reducing the effective brew pressure, similar to the expansion chamber design of the E61, albeit with the Speedster having more dramatic flair. In addition to the visual reminder of the piston moving outwards, the Speedster's preinfusion chamber emits a distinctive sound of hydraulic pressurization (it reminds me of the sound of an automotive hydraulic lift lowering).
I haven't measured the brew pressure profile of the Speedster, but will do so before wrapping up this review. Presumably the barista can combine the effects of line pressure (midpoint without pump) and the preinfusion chamber to produce a long, gentle pressure ramp. It certainly is effective, as I've found the Speedster is quite forgiving of minor errors in barista technique (the so-called "forgiveness factor").