Well I guess you actually knew that there wouldn't be any seasons but let's think about some of those effects.
Firstly temeperature ranges and daylight would be fixed, I guess that would mean that areas around the poles would never defrost meaning that the habitable part of the planet would be more restricted than it is today.
As for the plants - well they'd be much more like tropical ones, there wouldn't be deciduous plants and you'd probably not have any migratory animals and birds. We'd certainly not be eating the same crops
But the biggest change would be the weather. There are many seasonal weather effects like the trade winds in the Indian ocean that have played a huge part in our development.
I guess without the Earth's tilt the weather might be much more static than it is today not sure if that would be a good thing!