Yes....stupid question..but help me out

Ok...here's a stupid question, but since I'm new to the whole Honda tuner scene (it's my first Honda):

I know VTec is great. High school kiddies lust after it. Muscle car fanatics ridicule it. Honda doesn't put it in enough cars. But...um...when does it kick in? 3,500 RPM? 4,000 RPM? I've had my Del Sol (on the highway) up to 4,500 in fifth gear, and I didn't feel any sudden "boost". Don't flame me - I'm just wondering:

When does the VTec system kick in? Why can't I feel any noticable difference?

- General Dzur