i dont rate the ac2 as in highly, but it just does it job ok. It "simulate" a workable acoustic sound, but in no way sounding like real one. Work better with single coil than humbucker imho
other than the boss ac2/ac3, theres another from zoom. Its a multi efx with drum machine, A2. Its a acoustic geetar efx thou, but theres acoustic modelling patches in it. Cant remember how it sounds like coz its been a long time since i tried it with electric geetar. Only thing i remember now is the cheesy drum rhythm pattern in it to play along for indulgence.