The iQ is the monitoring system and also allows you to make the on screen adjustments to the Six-Gun really easy. If you also get the Speed Brake, everything is right there at our finger tips. In my opinion, it's worth it. My iQ and Bridge where both recently replaced a month ago, so far so good.
One thing to remember about the Six-Gun and Speed Brake, When you make settings changes, the Six-Gun and Speed Brake remember these changes. So if you disconnect and remove the iQ or the iQ crashes, the Six-Gun and Speed Brake will remember their last settings and keep on functioning none the wiser. So the crashing your hearing about with the iQ, is mainly an inconvenience, not a detriment to the vehicle.
If you opt to just get the Six-Gun, then you get a little knob that get's installed which will allow you to choose from levels 1-6. The Six-Gun will still function as well as it has always functioned and there are allot of users who run it that way.