I'd say "interesting" rather than good or bad, per se.
You'd have to define what "solved" looks like fairly explicitly, and the constraints about what constitutes a legal "solved" game (ie: Can pieces be missing from the board? Are only checkmates a legal "solution"? What about pawns making it to the end of the board?). A chess game is complicated enough that it should work for mining purposes though. That's just theorycrafting rather than any actual mathematical backing atm though.
Solved as in "generate every possible chess position, and then find the best move to play in any situation." A 1 MHz processor would take 10^90 years to solve chess, so we'd have no shortage of positions. My only problem is that there's not really a way to store all the possible legal positions, so it'd have to be really well distributed -or- a central supercomputer.