Hello
I have attended a few gigs there last summer (muse, snow patrol and radiohead) and they were excellent. It is wicked as a venue, has a really god festival type feel, and the bar is massive so you dont have to wait long. There are food trucks and things around too.
The portaloos arent the best, but they never are at outdoor events! the plus side is that you get the full benefit of the august weather, and being outdoors, you can smoke!
The transport between Edinburgh and Glasgow is great.. until about 11.30pm, which is when the last train runs. There are buses up until (i think) around 1am. There is plenty of cheap accomodation in Edinburgh, but if you did want to stay, i'd recommend booking soon as it can be VERY hrd to get something during the festival.
Meadowbank is about 15 minutes walk from the train and bus stations, and is 5 minutes by bus from the stations as well. There are loads of buses from the town to Meadowbank.
Hope this is useful. What gig is it?