I have just swapped a "wonderful" Canon 620 for a Canon i850.
The quality if the prints is better but the real difference is the speed.
It used to be that new menus for the Coffee House took me all evening. Now the job is done in under 20 minutes. It would be quicker, but I leave the prints time to dry before I print the other side.
I am saving myself 3 hours every time I do a reprint.
Your old printer may be good, but how much do you value your personal time at!