Informed opinion from the USA (which I cannot speak for myself) suggests that the lower speed of the Eclipse will affect upper airway routings over there.
As regards the report above from flying to/from southern France, I should say there is far less traffic down there than going generally east of the UK i.e. Belgium / Germany / Czech etc. Most French airports are pretty dead. The difference is even evident from the ease of working out Eurocontrol-acceptable airway routes: most autorouted Flitestar routes go straight through, but there is not a chance in hell of making them work straight off if going to the east. I've even had routes to Biarritz etc work straight off the paper charts, which is almost unheard of, from pilots who do not have access to the "inside" of the ATC system.