The G1XFOUR seems to be a direct replacement for the G1Xon. It is a good product, however it seems to be a downgrade in a couple of aspects that are important to me.
You can have 5 effects running at the same time. That sounded fine, but I didn't realise that also includes the amp, cabinet, and volume pedal! If you want to use an amp sim, cab sim and volume pedal, that means you only have 2 slots for other effects. This is a complete downgrade from the previous model which included amp sim and cab sim as one slot, and the volume pedal wasn't listed as an effect and could be used at all times. In the previous model, I could run Compression, chorus, amp + cab, delay, reverb and EQ, and it wouldn't have a problem.
If this doesn't bother you, then I recommend it, as the sounds from this pedal are still great. Unfortunately, I would like more effects to be run at the same time and this just doesn't do it.