I own both the GB and GBA Everdrive and both are fine for the most part except for games which need real time clock or accessories which the game need to work.
For the GB version, it make sense as they isn't any recent flashcard which can compete against the Everdrive. Most games work fine for the most part except those which use real time clock. The only issue I have to say when using the Everdrive is come down to which Gameboy you own. If it's the original and Gameboy Color, you should able to use the Everdrive but if you own the pocket, it won't work based on trying to use it on mine. I don't know if it's a common issue or just mine as I own a front lit mod Gameboy Pocket.
For the GBA version, it's still good but do know they is other flashcard (EV flash IV or V) can still do the same job as the Everdrive but much cheaper. Yea, they is some games which won't work on it but it's still cheaper at the end. Still, if you don't mind to pay the additional cost, then consider looking into it. If you can wait, wait for a bit as they is rumor of an update Everdrive for the GBA which should have real time save which the current one doesn't have. Not really a major issue for me but might be useful for certain people.
