Our situation is the opposite. The house feels more comfortable overall. Its still a little warmer upstairs where the home office and bedrooms are but generally around the house it feels a little more consistent.
You can definitely tell when the oil furnace kicks in as the air is noticably hotter. But when that happens the house gets warmer faster and gets a little too hot before it turns off again. And stays a little too hot for too long.
We went with a midrange system. In hindsight I do kind of wish we went with a different installer who was pushing a more "cadillac" type system where the fan (according to him) would always be (or just about) on but be variable in speed basically keeping the house at the right temp more often and slightly more savings.