It's great for NDS stuff and NES, SNES and GBA emulators (specifically written for NDS flash carts). Bad for battery life, but works great.
For 3DS games? Don't even try it. It tries to use Gateway's system and Gateway's code WILL. BRICK. YOUR. SYSTEM. Well, not that you could even attempt it on a 11.x sysnand anyway... If you happen to have 9.2 sysnand and 11.x emunand, you could get away with using the GW emulation if you installed an older Home Menu over the 11.x FW, and only used Gateway's 3.4.1 Launcher. Anything newer than that one and your system is toast.