The Red Box thief is different from the one in Heroes of the Fallen Lands, mixing at-will attack powers with at-will movement powers, and his backstab doesn't give bonus damage. Looks weak for a striker, but I haven't tested one in play so I might be missing something that's explained in the rulebook.
The transmutation wizard powers are good. There are no benefits for the schools of magic in the Red Box, however.
The fighter stances, cleric powers, and other wizard powers seem to be identical to those in HotFL.