I do 20 miles every day to work and i can do Monday to Friday on one tank of gas. My route is flats and hills and I average about 70-72 km/hr on level ground on my derestricted agility. Unless you tune them a bit they tend to be a bit sluggish uphill, mine used to drop to 15-20 on steep hills till i sorted out a few simple and cheap mods on the cvt, now i get up hills at 38-40mph or 30mph if its steeper, if its real real steep i may still drop to nearer 20 unless i get a run at it, but thats only on a real steep one.
The 2 stroke motors will have more torque generally so be better up hills but it depends how hilly your route is i suppose.
On the rental bikes, if i owned a rental company i would keep my bikes serviced regularly and be making sure i kept them running tip-top to make sure i would get my income from them. It all depends if it was a reputable hire shop or some cheapo back street place, if they took care of them and serviced them regularly they should be fine i guess.
Saying that, theres nothing like a brand new toy straight out the wrapper?