Still too early though he didn't live up to top ten status last year. Those folks (save quarterbacks) should contribute right away and in a big way.
As far as the comparison to Maybin, it's already over. Maybin did nothing...zero...zilch while he was here. Spiller contributed a few hundred yards rushing last year and had a 95 yard return for a TD. Those stats dwarf Maybin's 'contribution.' Hence... Game, set and match Spiller.
Obviously, Spiller's effort last year was nothing to get excited about. It just shows what an utter bust Maybin is. I expect a solid contribution/improvement from Spiller this year but given he will share the load with Fred he will not dominate statistically. It's hard to tell if he will ever 'live up' to that number nine pick. I'm hoping he runs well between the tackles, hits a few 'home runs' and shows he can pick up the blitz this year. It would give me hope for him going forward as a feature back. Otherwise, he will always be in that 'third down back' role.