Honestly I don't know if there is a big difference, unless he turns into a nutjob like Bush on foreign policy. I mean would I have expected two wars during the 2000 election?
The big issues on the table, pertaining to the budget and entitlements, will mostly be negotiated through Congress. Especially if there is a new guy in town without a lot of political capital (no way Romney is walking in with a mandate, even from his own party). Whatever deal is on the table, if Congress is behind it the President basically has no choice but to sign it and accept the mantle of dealmaker.
What concerns me most if that the Supreme Court will be dominated by hard-right conservatives. It'll really start to look lopsided in there, and with folks who aren't even mainstream conservatives. For them to want to wipe out the entire ACA was pretty extreme IMO.