I love Rotterdam...I lived in Zoetermeer for 4 years during High School and in a small town called Dieren from Kindergarten to third grade.
Rotterdam and Amsterdam in Holland, are the same distance apart as Rotterdam and Amsterdam in NY! Fun fact lol.
Holland in general is very flat, but great because you can ride your bicycle everywhere! Or get a Brommer(moped) and zip around on one of those...they are a blast. The people are generally friendly, and yes everyone speaks english quite well...you'll find you get much better help/service if you at least TRY to speak dutch. But they will instantly hear your accent and speak english back usually hehe.
Houses are generally smaller than average in the US, sales tax is crazy high but included in the price you see at most stores, other taxes in general are higher, universal healthcare works well there from what I remember about my few experiences with it in High School, and public transportation is great. You can take a train/tram/bus nearly anywhere.
Great open markets are all over the place with awesome cheeses, baked goods etc...mmm Olie Bollen.
If you can't tell I loved living in Holland both times, once in a small town, another time in a larger city. Two very different experiences but a blast. If you are an open minded person it can be great! Rotterdam has a lot of great areas! I prefer Den Haag and that area since there is a more international community and it's right near the beach areas. There are a bunch of fun small towns scattered all around between Rotterdam, Zoetermeer, and Den Haag though. If you need to be near the city for work but can commute by brommer/bicycle/public trans then i'd recommend maybe finding a nearby small town. Commuting by car can be a mess. I had a 30 minute commute by brommer in High School from Zoetermeer to Den Haag but it was fine.
Just read your other post...if you don't want to live in a big city I would most definetly recommend finding a nearby small town to commute from. There are bicycle paths connecting EVERYTHING!
Oh and it's fairly mild year round, but does rain fairly regularly from fall-spring.