So, in summary.
Pros
Very detailed. I was in a dilema as to say this was a con, for thinks like the airbox and injection system which will never be seen. There is a spinning fan inside the radiator cowl. I suppose the satisfaction is I know they are like this.
Alignment. Given the detail, it all lines up pretty well.
No painting at all
Lots of spare screws
No missing parts, although there are no mirrors or blanks.
Cons
Expensive, but I did get it on sale.

Most of the metal parts are very difficult to screw together and some screws bottom out. I had well fitting screwdrivers but it doesn't take much to round a screw off.
A few mistakes in the manual, strangely more as the book went on.
The instruction manual can be vague for the cables.
Can be fiddly, but the detail makes this inevetable I s'pose.
Some parts are hitting other parts, but everything I've done looks fine, so shouldn't be like this.
Misc
Some duplicate parts in the box, I'm assuming as the Pani R and Anniversario are basically the same kit, they have a base kit for each model, which these are from, then each kit has some bespoke parts, like the exhaust on this kit.
I'd probably do another bike, but I'm not interested in a car as it's the 1:4 scale and detail that makes it impressive. The cars I have seen are 1:8.
I still need to put the Marchesini decals on the wheels ans sort something with the mirror blanks.