If you want your pics to appear on other devices, or maca, then keep it on. I don't think that has changed at all. Beta just allows web access, I think.
Keeping it on would be smart if you have a mac. iCloud Photo Library does not sync with macs until the Photos app is released in early 2015. Leaving it on would allow iPhoto to import photos from your photostream.
On the other hand, if you don't have a mac (lets say just iPhone and iPad) then all your photos would be synced using iCloud Photo Library and you would not need photostream.