I've been in the private beta for a while now, using it for ad-hoc queries, still missing a few things I require but I think it will be better down the line!
Late reply, but which things is it missing for your needs? I work on the BigQuery team, so I can pass along any feedback that you have.
Have given most things in the Beta Group, First off I love the format conversion capabilities, just missing a few things like Clustering Algorithms. If parity can be achieved with the PostGIS ST functions then it will be fantastic!