So I was really discouraged by all the negative reviews of OBD Scan Tools.  There always seemed to be one thing that most people agreed they didn't like.  But realizing that in the last twelve months I've but over a grand into my two vehicles and following a real mess at a local repair shop where they argued with me about what I was told initially and even my paperwork, compounded by the fact that although it was a free service I was tired of going to my local auto parts store to have codes pulled.  I decided it was time to break down and make a decision.  Here's my perspective on these tools.  First, don't buy the "Swiss Army Knife" types.  If it seems like a gimmick, it always is.  Secondly, (and this is what I was hung up on) forget OBD I!  For most of us, our days of driving anything pre-96 is over.This tool (CP9580) had everything that I wanted.  It pulls, displays, and clears all generic OBD II diagnostic and trouble codes from all cars and light trucks regardless of make and model sold in the US.  (Though all scanners will as well.)  It does support ABS codes for the "Big Three" domestics.  This model is USB updateable which is still a rarity for some reason.  (Although I have yet to update it.  I will post again when I do.)  This is kind of gimmicky but the "code connect" feature give a list of a number of top reported fixes based on trouble codes.  However I'm not a huge fan of this since a code error from one system can obviously be a symptom of an issue in another system.  Finally it displays live data which I figure has already paid for the cost of the unit for me.  Following my less than pleasant experience referenced above with my 05 Lancer, about a week after receiving the car back I got another check engine light AND my idle was a little fast (but no code).  The according to the live data the throttle at idle is registering slight pressure.  The unit does not require batteries to operate, however it will work and store data when not connected to the vehicle with 4 AAAs.All in all, this unit (thus far) seems to be a well rounded device that is geared towards the weekend repairman.  It will save you hundreds if you have a few basic tools, the internet, and a little know-how.