I'm on my second Corsaro, having bought an ex-demo '06 bike and then traded it in in '08 for a new one. If I'm honest, the trade in of the '06 bike was because of a string of niggles (none of which left me stranded but were annoying). Before I took delivery of the new bike it had 30-something hours of updates carried out by 3x, and has been 99.9% perfect since day 1. When I rode it to the factory in 2009 (my dad on his veloce as well) we didn't take any tools or spares, and the only problem was a stone through my headlight (can't blame Morini for that! Hindsight and all- Ventura do lens protectors for the Corsaro- well worth the investment)
Having said all that, the factory and dealer network were incredibly good about honouring warranty claims, and even extended the warranty on early bikes to make sure everything was ok, so even an early bike should by now have all the updates. In short, yes I think you will find the early niggles are now sorted.
It sounds like you are aware of how great these bikes are, but sensibly are realistic about the potential for 'trouble'. Whether you should walk away or not depends which end of the scale you lie- if you seek Honda reliability then you may be disappointed, but if you're prepared to accept the odd niggle (call it character if you will) such as gear indicator occasionally not working, relays occasionally blowing etc then open your mind and soul to the experience.
I am not aware of any expensive horror stories such as engines lunching themselves, or Morini specific parts wearing out/breaking, and bottom line reliability is very good.
The most important thing when buying a used Corsaro is firstly to accept that currently the factory is not in production (should be soon though, all being well) so parts availability right now is patchy. This does however mean that it is very much a buyers market right now.
Given the factory situation then make sure that any bike you buy has all the factory updates done already. Don't assume that dealers can/will honour factory updates once production resumes. I assume that 3x can tell you what updates have been done on which bikes, but here is a useful link which shows the update bulletins for Corsaro and 9 1/2 (in German)
http://www.italobikes.com/de/foren/10-m ... -datenbank
Personally I would only buy a bike which has been looked after by one of the known Morini dealers. Sure, it's easy for anyone to service any modern bike nowadays but the approved dealers have access to the best tools and information to keep the bike in top order, which is well worth the money in my view.
In short, you'll probably find a Morini reliable and mainly niggle free, and you'll certainly tear around the place grinning from ear to ear. Buy the best example you can afford and remember that the updates were retrospectively applied so there's no reason to avoid an early bike provided the updates were done.
Tom