During the partial eclipse, the Sun is as bright as usual. During totality, no glasses are needed at all!
It's just as bright during totality, too, but the moon's in the way. :-)
Until ~two-thirds of the sun is blocked out, it's not as noticeable while you're viewing the progression... but yes, there is a dimming (think about it... there has to be since the sun's disk is partially covered). Once you get within a few minutes of totality, then the darkening gets quite pronounced. For sure: you wouldn't want to be playing baseball without the stadium lights on... which would mess with the experience for the fans.