It's generally fine. If you think of it half-way between a commuter rail/bus and a private car, you will do OK. After all, you sit on buses with other people, not much difference with Pool.
Once in a long while, the new route may be a mess and, when that happens, just get out and get yourself another car. It's so cheap that 1 in 40/50 trips like this is a drop in the bucket.
That said, don't use it when you are on a schedule.