I'm local to the area and have done runs in St Louis since my first full marathon back in '94 and this years GO! St Louis 1/2 marathon is the best course they've ever put out. The run starts out in downtown St Louis and you spend the first mile heading directly towards a bridge which brings you over to the Illinois side of the river then you come back over a 2nd bridge bringing you back into Missouri & St Louis. The two bridges actually make up a race within the race called the 3.5 mile Bridge Challenge which is separately timed and has it's own set of awards after the run.
The last 6 miles consist of an out and back course which goes to the historic Anheuser Busch Brewery which always includes a Clydesdale horse or two. The nice thing about the out and back aspect of the second half of the race was being able to see all the runners ahead of you which, this year included my brother going for his first sub 2 hour half :)

T-Shirt/SWAG - There was a very nice short sleeved tech t-shirt and classy looking medal commemorating the 15th anniversary of the run.

Aid Stations - standard, friendly nice people with GU around mile 8 or 9

Course Scenery - well, it's a city but if you've never been to St Louis before the skyline view when running back over into St Louis on the MLK bridge is pretty impressive and definitely worth the price of admission.

Expo Quality - Large Expo and very fun. There was a green screen near the entrance where people could get free photos of themselves either in front of the arch or the start of the race holding a medal or whatever they wanted. I posted one of these pics and mentioned I was in front of a green screen but, several people still congratulated me on the run.
Another booth had Ultra Sound where we could see the blood flow in our calves. The St Louis Track Club had all kinds of running shirts available 3/$10. It was a very well run expo and definitely on par with nationally franchised running events.

Elevation - I guess I just don't notice these hills as much as others so you'll have to consult other views & reviews on the hills. I thought it was all pretty reasonable.

Parking Access - for a race that commands 15,000 or more runners, I've never had a problem finding a parking spot. Either down on the river front or usually along Washington avenue I'm always within a few blocks of the start. No issues here.

Race Management - 15 years in the business and the GO! organization has several other runs they do throughout the year, from the GO! All American 5K (one of the best 5K's around) to the GO! Halloween Marathon, these people simply know what they are doing.

If interested in a more detailed review with additional pictures check out my blog review at http://icanrunaminute.com/2015/04/12/15th-annual-go-st-louis-half-marathon-review/