No, it's done in three stages:
Originally Posted by Palek
1. Plugin install.
2. Download binaries (bin.pk3) + global data (pak*.pk3) - this is the updating screen.
3. Download maps (all the map files like arenagate.pk3) - this is done in the background later.
So you get a "Play now!" button after step 2 finishes, but also get a tiny progress indicator on the top. If you connect to a server playing map that you haven't downloaded, it will be downloaded on priority. Whenever you quit the game, it will continue downloading everything else that's free, up until you're fully updated.
Premium arenas are downloaded automatically by premium/pro players. Standard players only download them on demand. The idea behind this is that you normally won't play a lot of premium stuff if you aren't invited, so it's better to save your time and bandwidth.
Practice games defaulting to premium maps are a clear bug, but minor (the game is an online shooter, that's the only part that matters).
Quake-Live QUIT SCREEN FIX Solution: Before you play on Practice, you must Play Online first, as that's the only way you can download the maps. (You can leave immediately after joining a match if you're in a hurry), then now you can play on Practice with the maps you've played Online.
Not the only way, you can download them:
Originally Posted by Duncan05