I have had mine done with a scanner too (not sure if it was called itero or not either!). For me it was not quite so easy, despite having a huge mouth lol.
Its very much like a hand-held barcode scanner as mentioned earlier, and so because I have all of my wisdom teeth through already, it was bloody hard to correctly scan in all of my back teeth. Just imagine squeezing a big ol' barcode scanner between your teeth and inside cheek, pushing it far back enough and angling it correctly to take pictures of your wisdom teeth... it got pretty uncomfortable!
But to manage your expectations, the dentist told me it usually takes 20mins to do, with his quickest time being about 10mins and longest 30mins. Mine took about 40mins lol. But hey at least it was thorough, and its not like it hurts or anything!
The system is great though - the scanner is hooked up to a computer, and the software will highlight any areas that have not been scanned properly (or any questionable gaps in the scan i.e. where it thinks the scanner might have missed out areas of your teeth or if the gumline was missed). So I can only imagine it is way more accurate than moulds, which can probably distort quite easily and is at risk of damage when being posted (the scanned images can obviously be emailed instantly!).
The only thing I don't really understand is how the scan knows the actual dimensions of your teeth (i.e. how does it know a tooth is 2cm long and not 3cm long... technology eh...!). Either way my invisalign ultimately fit well so I'm happy. The real test will be how my teeth look when I'm debanded next year!!
For now at least, would definitely recommend scanning over moulds.