This has been reported on the beta forum by somebody else, and is apparently a problem for Nexus devices running 8.1 too.
The problem is that the WiFi hotspot allows devices to connect to the hotspot and assigns them an IP address but the devices then have no internet access. I can ping the phone from a connected hotspot device.
Please see the post by "jaffa" here: https://community.phones.nokia.com/support/discussions/topics/7000015662
Any update on getting this resolved would be very welcome, I use this feature a lot.
Also facing this problem, this is a major problem for me, may have to return the phone.
It was working fine under 8.0. Current ISP does not allow chaning APN type string, so that fix that's floating around is a non option.