There’s no one perfect piece of luggage, but for adventurous travelers. the Eagle Creek Switchback comes pretty close.  By converting from a wheelie to a backpack, and featuring a full-sized zip-off daypack/backpack, the Switchback Max offers maximum versatility in mobility, while still meeting regulation carry-on requirements.  Outside Magazine named it a Gear of the Year product for 2005.  The 22" model meets most carry-on restrictions (with the daypack removed). Buy it for $279.99 with free shipping from Backcountry.com. The 25" model is $299.99 from Backcountry.com.