I should start by stating that I have no professional/financial interests in either Gendan or Shop4parts but I can very strongly recommend both organizations to anyone on here. Gendan gave me a lot of help, as did forum members, when I was thinking about buying a licensed copy of
MES and then, when I finally took the plunge and bought it from them, I ran into problems configuring the computer to communicate with the interface - I went for the Muliplex option, a bit expensive but well worth the convenience in my opinion. Both Gendan and Forum members were very helpful in helping me resolve these issues. I think
MES is the best value for money when it comes to FIAT diagnostics and lets you do pretty much anything, by way of diagnostics, that the competent home mechanic might aspire too. One of the big problems with vehicle diagnostics is acquiring the knowledge/experience to effectively use the information it gives you and
MES is very good at giving suggested actions/fault procedures etc on the right hand side of the page. The best thing to do after you've bought it and got it set up, is to plug it in and "play" with it. I especially like graphing sensor outputs and it's very handy to know what a good trace looks like when looking for a fault.
So what's S4p got to do with any of this? Well very little really but I thought I'd drop them in here as they are one of my main "go to" sources not just for good quality FIAT specific parts - although I tend to buy simple service parts from my local factor - but also because they are very approachable and helpful when I'm trying to source something "difficult". You can just ring them up and they freely give good advice without being too "pushy" or trying to hurry you too much. Between them Gendan, S4p and my local factor (SRS) let me deal with at least 95% of what I do with the "Family Fleet".
Edit. By the way, I completely agree with s130 above when he says to go with a cabled connection. All my stuff, including my VCDS (VAG-COM in "old money") is cabled. You'll really, REALLY kick yourself if you ever loose connectivity when half way through some of the more complex procedures!