Just went last week to First Friday in September. Definitely worth going to.
Parking - Pain in the @#$. Find a lot and if you have to, pay $5. This way your car is safe. Parking on the street is a do at your own risk proposition.
Food - Note to self, lots of food trucks, but if you see there isn't a line for their food, go to the next truck. No line= food sucks. Line = worth the wait!
Art - Plenty of good, bad and ugly things to see, but its art, so its subjective. There's a bit of everything for everyone.
Music - Sometimes there are bands, and last week there were some street performers and another area with a DJ. Can be a bit of a hit and miss.
People Watching - Wow, now this is why you go to First Friday. Where else can you see folks dressed up promoting "Fairy Fest". Then you have tattoo artists and all sorts of folks pitching their wares. Ah celebrate diversity!
Overall- Worth checking it out, but do it when it's cool out.