Friends of Mineral Town is not just an excellent portable version of Harvest Moon, it's practically a remake of the Playstation entry in the Harvest Moon series, Back to Nature
The first thing you'll notice from playing Harvest Moon: Friends of Mineral Town, is that it is almost identical to Back to Nature. The game is done in overhead 2D instead of isometric 3D with rendered sprites like Back to Nature, but the layout of the town is identical and the characters and their personalities and associations are the same as they were in Back to Nature (and not Harvest Moon 64).
But that does not mean that the game is just a port. The game is set up so that you do not have to accomplish anything in a year. There is no set goal except just to enjoy living your life on the farm.
Due to the limited buttons on the Gameboy Advance, the controls for Friends of Mineral Town seem a bit awkward. In the demo, you can't switch tools with a button press, instead having to bring up the status screen and manually change weapons. You can't switch between the item you're holding as well, and unless they fix this, this will make loading vegetables into the crate a hassle. Since a lot of options were unavailable in the status menu, it seems that the controls are still early and not final. Besides the current control figuration, movement is fairly smooth and the ability to run by holding the R button makes moving more convenient.
One of the problems I've always had with previous Gameboy versions of Harvest Moon is how limited they were in terms of character interaction and farming aspects. Harvest Moon: Friends of Mineral Town is the first game in the portable series to be on par with the console versions, gameplay-wise.
The bottom line is that if you are a fan of Back to Nature, you will absolutely love Friends of Mineral Town, since it's practically a new version of Back to Nature.