The Mega SD just had a firmware update adding support for the Genesis version of Virtua Racing, making the Mega SD the only flash cart to support that game.
I still haven't ordered one, but my resistance is dwindling, especially as early reports are extremely positive, at least from what I've read.
To remind myself how little I need to spend money on a new flash cart, I've been playing some Sega CD through emulation. I gotta say, Snatcher is overrated.