As always, I think the D&D class/level structure is a completely false and antiquated system. It is a straitjacket that was imposed in the first RPG and has only been enforced by D20/3rd Edition. I would much rather play in a classless system, such as Hero or BESM's Tri-Stat.
All that being said, I'm not keen on the idea of having to learn and purchase a whole new game system (Runequest.) See, I'm OK if nobody else knows how to play a system I already own, but I certainly don't want to have to buy one myself.
(Obviously, I am joking. I have spread around several copies of Tri-Stat Dx, Silver Age Sentinels D20, Traveller and Hero's Sidekick book to members of the group, just in the hopes that we could play another system and that no one would have to buy a book. In fact, after Christmas I may pick up a few copies of the new Mutants & Masterminds pocket player's guide, just so I can seed the group with copies.)