I am reviewing the Autel MaxiScan MS509. I had done a considerable amount of research on ODB-II scan tools.  The big consideration was do I look simply for a code reader and reset device OR do I look for a real-time diagnostic tool.  I had no less than six different models from various manufacturers on my "short" list.  Previously in the automotive repair industry I was familiar with the protocols with OBD scan tool devices.  I spent time reading Amazon reviews, OBD forum sites, youtube etc.  [I went through a lot of Visine from staring at the PC monitor for extended periods!]. I went with this model largely on credible reviews, features and price. Amazon's price is respectable but if you dig into the issue you will be able to find one thru an importer.  I got mine direct from where they are made overseas [$60].I just received it and these are my initial impressions: Good heft and build quality, feels like a real "professional" grade tool, came with all the accessories you should need except 9V battery.  I hooked it up to my wife's '99 Jeep GC which is supported by SAE J1850 protocol and was able to quickly navigate the tool set up and DTC scan/test options.  The live data stream mapping is a great feature.  I will be trying it out on my '09 Dodge Ram which is CAN supported and should get even more information from that protocol.  This spring/summer I plan on scanning as many of my friends and neighbors cars that I can to get proficient with it.  I will make occasional updates as I work with this tool.  I know some folks have had issue with specific scan tools, the only bad thing about reading too many reviews is that after awhile one goes into "information overload" and you have a hard time making a decision.  So far I think this is a solid choice, I'm not saying there are not better choices so don't get all wound up if you disagree with me.  Tech. has come a long way from 10 years ago which was the last time I used a shop-owned scanner that my employeer paid $4500. for!  It was a Snap-Off brand and at the time thats what they were all going for, all the updates were with plug in modules [$100 plus each!] that you had to buy from the traveling tool rep.  Now updates are via the internet and usually free or low cost.  That eliminates the middle-man and his mark up but it reduces good customer service since you are dealing with a corporation five states away that does not give a rat's A@@ about you [usually].  I can't speak to Autel's customer service yet, but I did send them an email yesterday requesting information on the latest firmware updates available....we will see what the outcome is.  If anyone wants any other [specific] information I will do my best to answer.