It's incredibly useful for utility spell selection.
For example, in our last session we were exploring the underdark when the party approached a lake we needed to cross. We "befriended" a koa-toa, but there was no way that my craven cleric was going to get in a fish-man's boat without some insurance. We asked him to wait a few minutes so I could cast water walk.
Later on this had a huge payoff. A group of koa-toas attacked us on a large staircase on the other side of the lake, and one of them bull-rushed the party wizard over the ledge into the lake. The koa-toa fell into the water expecting the weak land-walker to fall in with him...