There is permanent seating towards the back of the main floor and in the balcony .. and that you do indeed 'grab'.
The sound is excellent anywhere I've tried, so it's a matter of where you'd like to be.
The large raised bar section also has standing room .. and often a batch of the loudly, continuously, yakking types, so if that annoys the crap out of you (like it does me) you might want to stay away from that area.
BTW .. if you plan on having 'adult beverages' be sure to bring your driver's license or some other photo ID with birth date. Everyone is carded at the door - you won't get the wrist band w/o ID.
If the same food people are there, don't worry if you're running late.. they have some good light food .. including an excellent roasted veggie slider.
And on that topic .. there are quite a few restaurants w/in an easy walk of the venue if you want to come early to get parking.
You can park on the street for as long as you want after 6:00pm * .. and there is a parking garage just around the corner if you don't mind paying.
State Theatre is a very old venue that was completely renovated and reopened in 2010. An owner of Higher Ground (Burlington) is a partner and they did a superb job. I think you'll like it.
* I use the garage, but I'm pretty sure it's still 6pm. Will ask a Portland twitter buddy to verify that before the show dates.