Buying a new aircraft - you will need to be brave!
The biggest risk: putting money up front and the company going bust. No idea what the laws are in foreign countries and what rights creditors have - and how one would enforce them. So a lot of cash hanging out there for quite a while.
Delays: don't worry about 12 weeks late without penalty. It would take you more than 12 weeks to go to court abroad to try and force any contract!
Engine: we have had a new 912 sent from the aircraft manufacturer in Germany. Small oil leak. Skydrive - the UK agent - said: speak to the people in Germany who sold it to you, they are the ones who got the profit from selling it and so should give you the service. Totally against EU law and good customer service. Anyway, a few months later the hangar went on fire and it was all an insurance write-off..... so never got to the bottom of the oil weep of my EU rights.
Warranty: well, six months is OK, should have found problems by then - and if there are major design problems, others will have found them out by now. Do your research. Beware, if someone finds a major problem, company may not be able to survive the warranty claims, however long a period they stated. (see history of Scottish wind turbine Proven for an example!)
My thoughts. Glad people do buy new, it makes buying second-hand easier for me!