Tbh we already saw Ichigos Bankaiagainst Ulquiorra to be honest. It does whatever his old Bankai possibly 10x more powerful.

• Massive increase in his speed

• Increased swinging power.

• strong enough to bare hand lighting bolts which can nuke massive areas.

• Gran Rey Cero with huge destructive capability

• High speed regeneration

As far as we know like many of the young soul reapers he never completely mastered this power even in the end.