I went the same route. I owned two gas motorhomes and decided to upgrade to a diesel pusher. I bought a new 2009 Monaco Cayman. As mentioned by others, there are problems with the stock trailing arms. It is imperative that you have upgraded to the improved Roadmaster trailing arms or (preferably) the Source Engineering upgrades. I went with Source Engineering and also installed their Ride Enhancement Kit. I'm a full-timer and have over 36,000 miles on mine.
My ride is now very good... much better than my previous gasser's ride. For comparison, I drove my buddie's 2006 40 foot Allegro Bus and while the Allegro better on the bumps... not by a lot. Mine actually makes less noise when it hits a big rut! My RV no longer has any porpoising and handles bumps/ruts well. The big difference I noticed versus the Allegro Bus was how it handles in the wind. I think that may have more to do with it's steering box and chassis.
Don't get me wrong, a four bagger will never be as good as a eight bagger... but I didn't want to shell out the additional dollars for it. I'm sure that a lot of folks with eight baggers would like to have a ten bagger... or a Prevost... but don't have one for the same reason.
Good luck with whatever you decide!