Galaxy S4 Wi-Fi Issue
I also got one last week and am seeing similar problems. My hub works very will with every other device, but the S4 continuously disconnects from it, even with a strong signal. It will even stop receiving data in the middle of a stream while the wi-fi incoming arrow still flashing.
I brought it to work and it stayed attached to wi-fi for what seemed like an extended period, but I'll need to keep testing to be sure it's a compatibility problem between the S4 and the hub.
I tried some of the tricks recommended for S3 wi-fi issues (disabling low-power mode, turning off auto-connect to AT&T, removing the battery), but nothing is fixing this issue.
One would think the standards are fairly, well, standard. The S4 seems to have an issue where other devices don't. The S3 seemed to have some as well...