This is a great product. I only really have the Everdrive GB X5 to compare with. In terms of quality/reliability and functionality the Everdrive series doesn't compare to other flashcard solutions.
That being said, Action Replay / Game Genie code support would have been a welcome addition. Then again, this card allows the use of romhacks and homebrew of which there is plenty on GBA.
Minor issue was that the microsdhc loading mechanism appeared unreliable at first. I had read online before purchase about compatibility problems, so I bought one that was compatible. Long story short - that SD card was bad. It works fine with all my microsdhc cards. The physical loading mechanism sometimes requires a pull after the push to eject - maybe 1 out of 20 times. But this is a really minor detail.