Pretty good although you need to stack on IAS items for it to proc as soon as it's out of cool down. I may be wrong though the chance to land an Entangle and Bash is parallel with each other - meaning that it can proc at the same time.
Other than that, it just slows your Radi farm or by the time you have acquired a Radi, the game has come to a point that it barely does anything.
Mostly, Spirit Bear's core are Phase Boots, Assault Cuirass, and Radiance. Anything you get on it are considered luxury. If I have the excess gold, I prefer Gloves of Haste or Hyperstones for more DPS and a better chances of landing an Entangle.
The better focus is building Syllbear, himself, to be survivable during the later stages of the game. For trolling purposes, you might wanna grab a Shiva's Guard, Eye of Skadi, Sange and Yasha, Boots of Travel, Butterfly, HoT on Syllabear. That set provides good EHP but barely does anything in escaping.