Paritiioning really isn't a performance tool. Even if you write queries that work against only one partition, that partition will still be on a single file space and will act no more differently than if all the data was on a single partition. Depending on the query, it might not even help if you always end up with scans instead of seeks. Sure, you can get some benefit by doing things like putting indexes on a different physical drive space than the data but nothing will ever make up for not having a good database design and writing good queries. The horizotal partitioning that we're talking about is to ease maintenance time by making it so that you don't have to reindex the whole of a table.

Partioning of data is not a performance panacea.