I’ve done it.
A great day out. The locals are very enthusiastic and helpful.
You start with a long road section. If you’re at all interested in a fast time, you need to make sure you’re near the front when that ends as you’ve then got a narrow, steep off-road climb. Lots of folk will be walking and you’ll not find a way past.
Quite a bit of climbing during the day and I certainly had tired legs by the end.
It’s worth staying over a few days to make the most of the rest of the island. If you have a road bike, take that too and do the TT course.