My reading was that columnar storage was a critical piece of Dremel. "Accessing the same data as Hive" doesn't sound like Impala is doing that. Is that optional then or is this just a query engine?
I can't say for sure, but I believe Doug Cutting's Trevni format is already in the beta but it's a slow version. Impala is initially focusing on architecture, I'm sure columnar format will have attention eventually.