Dan, glad to hear you got your interface box and that you're happy with it. By now, you realize that its much more than just a scanner that outputs DTCs... it gives you real time access to some of the engine management data stream... as well as letting you see the output of a number of sensors (air mass, temp, etc) under the hood. You gotta try it with a laptop while somebody else drives the car... neat to see the system in action.
I understand Steve's point about much more being available if you have the proper tools and knowledge... but you'll have to agree that 10% knowledge of what's going on under the hood is 100% better than 0%. I would never pretend that this tool would take the place of other gear. For that matter, I don't think any amount of tools will ever replace knowledge and experience.
He's also correct (of course) that it doesn't do diagnosis... but, it sure has helped me track down some problems. When the CE light is on, the DTC says the mixture/trim is out of spec, and the output plot of an O2 sensor is flat, I think that's pretty compelling information for diagnosis of the problem.
Additionally, for guys that want to understand what the engine management controls do and see what the outputs look like, its an invaluable training/learning tool IMHO. I really like the displays and the plotting capability.
As I said, I've had my interface for some time now... and am now looking for a good used MT2500 so I can learn more...
Yep, like learning to read... but, you gotta begin somewhere... and the price is right.
Just my 2 cents.