Semi-related:
Is it possible to boost skills beyond 100 points?
I bring this up because I just found the http://elderscrolls.wikia.com/wiki/Notched_Pickaxe.
I did test this myself, and I didn't seem to see any difference in improving my armor. Also note that the wikia page for the pickaxe specifically states that it can't be improved over 100.
Just want to verify with you guys, thanks!
EDIT
Thanks for the quick answers. Not only is it possible, you can disenchant the Notched Pickaxe and get 10 extra smithing points by enchanting it onto 2 weapons we can be dual wielded.
Best Answer
Yes, smithing over 100 has an affect on upgrading. In this answer I raised smithing to 130 via two items. That allowed me to increase the armor rating from 528 (@100 smithing) to 610 (@130 smithing).