Is Parallel Data Warehouse feature of SQL Server 2008 R2 targeted only for OLAP/BI impementations?
Can we use it for hosting OLTP databases as well?
ABSOLUTELY NOT!! It is purpose built from the ground up for large scan aggregates.
What you MAY want to check out is Hekaton. If you have seriously high transaction volumes MS may let you in on the TAP.
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru at GMail