I use a Briggs and Riley 20" wheeled carry on. They are as tough as they come (as good as Tumi), seem to have a bit more space inside than the Tumi equivalent and come with a lifetime guarantee.

I also have a 21" expander which in its unexpanded state is just too big for the new regulations, but has found its way past the LHR baggage police on several occasions without comment or challenge.

Both of mine have done many flights and still look as good as new.