Location: Back to the Buffalo. At least I'm close to Toronto.
Programs: Hilton, AA, SW, Delta
You can get Hilton Gold after 4 stays using the MVP rate. Check the Hilton forum for detail. Hilton Gold and Diamond get free internet at all hotels.
Early check-in is usually not a guaranteed benefit but at the hotels discretion. I have checked into hotels at 8am with no extra charges. It really depends on the hotel and if the room is ready to be occupied.
Programs: AA 2MMEXP, BA Gold, UA 1MMPremierGold, Hyatt Diamond, IC RA, SPG Gold, FPC Plat, HHonors Gold
The only guaranteed early check-in of which I am aware is for Royal Ambassadors at Intercontinental hotels, and that status entails a referral or far more than "a few" stays. Like the poster above, I've been able to check in early at many hotels in other chains or independent hotels, but that's a function of availability and is unlikely if, for example, the hotel has been full the night before.
If it's that imperative, why don't you book the hotel for the night before?