I feel like this has all been discussed before (likely on this forum). The Diavel is an opportunity for Ducati to widen their client base. Those of us who have Monsters aren't their demographic, but guys looking for alternatives to heavy cruisers (HD and such) likely are. It's certainly not for everyone, and that's cool, because there are plenty of bike choices out there
I've seen a few Diavels out and about and I was really interested in who was buying them. Both guy's I managed to speak to were remarkably similar in that they had both always ridden big jap sportsbikes but got into there 50s and decided it was time to get a cruiser (well, each to there own). Not happy with any of the japanese cruisers they test rode a Diavel and were completely won over, bought there Diavels and are total converts, they couldn't speak highly enough of the power, handling, braking everything. So, more power to Ducati I reckon.
About the looks, I think you got to compare them against other cruisers
, not other Ducati's. In a pack of Japanese cruisers, the Diavel stands out like a big shiny diamond.