The Gameboy micro is a nifty little system (emphasis on little) that is much smaller then both the original GBA, And the GBASP, It had both up sides and down sides.
Ups
1: Size: Its small size makes it very easy to carry and comfortable to have in your pocket. It is very easy to take to and from places, and does not weigh much. Its size is also a bit of a downfall as well, you will read this later.
2: Screen: While small, it is still a nicely backlit screen, making it easy to see what you are doing in the game. The screen is also a bit of a downfall, you will read why later.
3: Individuality: Possibly the coolest part of this console, was the customization. The GBA Micro had removable face plates rather then a fixed plastic screen protector, meaning the face plates could be changed to ones personal tastes. This was probably due to the fact the console only came in black, and a 20th anniversary edition, which was red and gold, where most gameboys came in several different colors.

Downs
1: Screen : While it is a nicely backlit and easy to see screen, It is very small, Much smaller then that of the original advance and advance sp, and may cause your eyes to tire quickly.
2: Comfort: For a child of a young age, this system may be more comfortable to hold then the bigger GBA, and possibly gbasp. However for people of average size or larger in their teens and adult years, system can quickly become uncomfortable to hold due to its small size.
3: Backwards comparability: If you are looking for a cheap console that is able to play gameboy, gameboy color, and gameboy advance games, this is not for you. this gameboy will not play original gameboy games, as well as gameboy color games. You are better off with a AGS-101 model SP, or a AGB-001 model gameboy advance.
4: Accessories: Finding accessories for this system is very very difficult. This model of gameboy used a different charger, link cable, battery, everything. You can not use a GBA Link cable with this, you need to find an adapter. If you lose the charger, you will have a rough time finding a new one, because the console was short lived and seen as a bit of a failure, so 3rd party support was small. Faceplates are hard to find, it uses a different battery that is soldered to the motherboard, rather then the 2 AA's the GBA used, or the removable rechargeable battery the SP used.
5: Price: For what you get, this console is expensive however you look at it, if you are a collector in the market for a brand new 20th anniversary model, then that's really all this console is good for. Used, they can be $50-$70 USD or more, and can be only in playable condition with some nasty marks and missing parts.

Summary: The gameboy micro was a nice idea by nintendo, however its high price, even used, lack of 3rd party support, and lack of ease to replace parts if needed, makes this a console one should try to avoid unless one is a serious nintendo collector. If you want a system to play both GBA and GB games, either look into a gba sp ags101, or a gba agb001, or possibly a custom backlit gba agb001 for the extra comfort.
The Gameboy micro is a nifty little system (emphasis on little) that is much smaller then both the original GBA, And the GBASP, It had both up sides and down sides. Ups
1: Size: Its small size makes it very easy to carry and comfortable to have in your pocket. It is very easy to take to and from places, and does not weigh much. Its size is also a bit of a downfall as well, you will read this later. 2: Screen: While small, it is still a nicely backlit screen, making it easy to see what you are doing in the game. The screen is also a bit of a downfall, you will read why later. 3: Individuality: Possibly the coolest part of this console, was the customization. The GBA Micro had removable face plates rather then a fixed plastic screen protector, meaning the face plates could be changed to ones personal tastes. This was probably due to the fact the console only came in black, and a 20th anniversary edition, which was red and gold, where most gameboys came in several different colors. Downs
1: Screen : While it is a nicely backlit and easy to see screen, It is very small, Much smaller then that of the original advance and advance sp, and may cause your eyes to tire quickly. 2: Comfort: For a child of a young age, this system may be more comfortable to hold then the bigger GBA, and possibly gbasp. However for people of average size or larger in their teens and adult years, system can quickly become uncomfortable to hold due to its small size. 3: Backwards comparability: If you are looking for a cheap console that is able to play gameboy, gameboy color, and gameboy advance games, this is not for you. this gameboy will not play original gameboy games, as well as gameboy color games. You are better off with a AGS-101 model SP, or a AGB-001 model gameboy advance. 4: Accessories: Finding accessories for this system is very very difficult. This model of gameboy used a different charger, link cable, battery, everything. You can not use a GBA Link cable with this, you need to find an adapter. If you lose the charger, you will have a rough time finding a new one, because the console was short lived and seen as a bit of a failure, so 3rd party support was small. Faceplates are hard to find, it uses a different battery that is soldered to the motherboard, rather then the 2 AA's the GBA used, or the removable rechargeable battery the SP used. 5: Price: For what you get, this console is expensive however you look at it, if you are a collector in the market for a brand new 20th anniversary model, then that's really all this console is good for. Used, they can be $50-$70 USD or more, and can be only in playable condition with some nasty marks and missing parts. Summary: The gameboy micro was a nice idea by nintendo, however its high price, even used, lack of 3rd party support, and lack of ease to replace parts if needed, makes this a console one should try to avoid unless one is a serious nintendo collector. If you want a system to play both GBA and GB games, either look into a gba sp ags101, or a gba agb001, or possibly a custom backlit gba agb001 for the extra comfort.