In relative terms it will always be compromised on luggage and comfort compared to almost any big quality saloon. That said no problem at all in long distances. Pack carefully and think of the journey as a key part of the trip.
Incedentally I've drive competition Jeeps to the South of Spain and Artic circle and was brought up in 1960's cars crossing Europe (read plastic seats, no aircon, etc.) so the Zed is sheer heaven to me over any distance.