I'm actually driving an '94 Integra LS now for a bit, not my most favorite car in the world. Gas mileage could be better, 23ish city. Get a civic if your looking for amazing gas mileage. And sadly I like driving them more.
However, the LS's take very well to turbos and you could pretty easily have around 200whp fairly cheaply, and reliably.. The LS/VTEC swap requires machining work i believe, and if it isn't done properly the engine won't have a long life.
I've been researching this stuff cause I've thought about modding it... then i just can't justify spending money on it other than maintenance. Not a bad DD though. I say go for it if you like it enough.