In the 3yrs I used Altium (v16, then v17), Altium would always have horrible bugs, and they never got fixed. They would introduce new features (yay!), but new bugs would get introduced, in addition to old bugs that never got fixed (boo!). Horrible bugs, like the whole application crashing if you clicked outside of a dialog box or something, or sub-dialog boxes being blacked out for no reason. I really like the interface, but Altium is almost bloat-ware in my opinion. They should really focus on fixing bugs rather than adding features.
If I were you, I wouldn't use their beta software at all...let other people be the guinea pigs and wait for official release...maybe even a 18.1 release so all THOSE bugs can get fixed (yeah right...)