I haven't had issues with AT&T but tons of issues on wifi both home and at work. Work wifi seems to not to like App Store at all, I can view things in the App Store and the downloads to try to start but then stall. Same with iOS updates.
It carries over to home as well, where I had to full restore my phone last night to get it working on home wifi again to download apps or check updates. Both cases cell worked. Resetting network or all settings did not work, only the full restore. Home works now, work still does not.