Hi Roman, good point. I think for now it's ok for us to change the user to hive user. Having 2 separate users would have puts some restrictions on the permissions of hive warehouse directory on HDFS and the embedded derby file based storage on local filesystem at the very least. Changing to hive user should fix those.
I have been thinking about this a little more and I think moving forward, it would be really nice to have a standalone RDBMS in Bigtop which we can use to house all metastores (hive, oozie, hue, etc.) in Bigtop. I will create a separate JIRA (for Bigtop 0.7) for that but when that happens, perhaps it would make sense to revert back to HCat user since we would no longer be using embedded derby and can easily manage the permissions of hive warehouse directory on HDFS.
You have my +1 (non-committer).