Are they compatible?
Yes, the CycloDS Evolution is compatible with both the original 3-in-1's, as well as the more recent 3-in-1 Plus.
3-in-1 Plus Known Problems
Be aware that if you bought a 3-in-1 Plus and it is not working correctly, you may have a defective unit, as many of the first batch did not work. You can ask here or on the Team Cyclops forums if you're not sure, and it may end up with you needing to return it to the store you bought it from for a replacement unit.
Problems running GBA games
This problem has been fixed as of firmware 1.57 STABLE. If you are unable to boot GBA games to NOR memory, but every other feature on your 3-in-1+ works as expected, please consider upgrading your firmware.
• Dump your DS/GBA games
• Can I play GBA games without a Slot-2 device?
• GBA Flashcart Compatibility
• Can you play DSiWare games on the CycloDS Evolution?
• Saves not working? Change your EZFlash 3-in-1 battery!