This has three implications:
1. The wizard carrying a sunrod can't move in 'double time', but only one move per turn.
2. The wizard movement speed is likely reduced from 6 or 7 down to 5 over any period of multiple rounds, or he out paces his mage hand.
3. To keep carrying the sunrod you need to walk up to where it is with your move, and then move it ahead. If using the mage hand to illuminate the path ahead it means the wizard is going to need to be pretty close to whatever he illuminates by the time the sunrod floats forward (assuming 40' shadowy is 8 spaces plus 5 spaces ahead is only 12-13 spaces). And, since the last action is to move the sunrod by necessity, by the time he sees the creature his actions will be over.
All in all a very cool utility spell that I'm looking forward to seeing players use much more than prestidigitation ever was.