There's going to be a problem with a lot of UIs. The one I'm using now on live has been my baby for a long time, but on beta the main-bar is non-functional. It's due to them adding the auto switching to the bars for mounted combat and I'm not skilled enough to fix it. My concern is that if there isn't a fix found by a coder, there's going to be a lot of people with custom UIs flaming Turbine for breaking something (Turbine) still considers in beta.
This isn't a rip on Turbine as multiple skill setups is a nice feature for people that don't use plugins or custom UIs. For those that do there are growing pains for us from time to time.