My new 3DS XL has FW 4.4 on it. I understand that if I want to use a flash cart for 3DS games I need to keep this firmware, I'm wondering though what features will be locked away by not having the latest firmware. I already know about the eShop.
Pretty much anything that requires global wireless connection will be out of reach. Such as downloadable contents, game fixes/patches, firmware fixes/patches, global online gaming, etc. You'll just be limited to local wireless among friends in a same room/place as you are.