Hi - I'm from Gateshead (other side of the river) and originally from Sunderland (other side of the divide) - you will no doubt learn all about this when you arrive and have it impressed upon you!!
The nightlife is second to none, Newcastle is a world of its own, loads of cool restaurants and in the Stowell Street area of "The Toon" lies China-Town - although it is a city of course, Geordies fondly refer to the city as "The Toon" - mainly because they can't speak correctly, and everything revolves around their mediocre football team - third best in the area after Sunderland, and Sunderland Reserves
Can't tell you about the gyms - I don't think they have them as most Geordies are beer-swilling obesers, and truancy is the national sport - so no schools remain north of the river Tyne.
It's a little more lively than a Saturday night in Stroud
Most of the above is of course based on the legendary Tyne-Wear rivalry and of course Newcastle is a fantastic place - even speaking as a Wearsider myself.
I'm sure some of the Novocastrians will be along soon, but they're probably all at the Bigg Market tonight, so might be some time.
Oh and great shopping, theatres, Arenas, railway station & international airport - as well as the fastastic Metro system to transport you around.
Hope that helps a little.
Steve