I just downloaded a trial and have immediately run into problems. I have windows 7 x64, and 64 bit drivers connected to a remote Greenplum database.
The first problem was Tableau would not connect to Greenplum, even though I could connect to Greenplum in OBDB, Excel, PowerPivot, pgAdmin III and Aginity Workbench just fine). Tableau gave an driver mismatch error, so I had to go download 32 bit drivers for GP.
This enabled me to connect, and I also tested the 32bit connection in ODBC and pgAdmin III and everything ran well.
In my tests, I picked a very small table (~5000 rows) and GP retrieves them in milliseconds (in the other tools). However, when I use the live connection in Tableau, this runs several MINUTES.
What is going on? I cannot find any other comments on this. Even the "View Data" takes at least 3 minutes (compared to <1 second in the other tools.