Judge Alito, if confirmed, could have a very profound effect on gun control, considering his views concerning the use of the commerce clause as a foundation for federal gun control. His dissent in US vs Rybar challenges the legality of the machine gun clause in the 1986 FOPA, and perhaps illustrates how he feels about all federal gun laws; assuming a case, or cases regarding firearms legislation reached SCOTUS.

A quick look at handguncontrol.org illustrates the concern a prominent anti-gun organization has regarding his position.

I dont really see Alito's inclusion affecting US v Miller, since there is little evidence he dissented in Rybar because he believed the 2nd amendment voided the machine gun ban, however the opinion in the dissent gave an equally valid, and sweeping reason for ending a great deal of federal legislation. That is however, not saying that he might hold a very diffrent view of the second amendment from the one indicated in Miller, and Emerson.

I'd just like to note that this might not be the best forum to discuss the positions of Judge Alito on other issues such as wire-taps or abortion.