Where can I find more information about BW 7.5?
The following link takes you to the SCN landing page for BW 7.5.
The latest BW Roadmap covering all new BW 7.5 features you can find here.
I heard there are two versions of BW 7.5. Is this true?
Yes, that is correct. BW 7.5 comes in two flavors, the standard SAP BW 7.5 powered by SAP HANA, and the SAP BW 7.5, edition for SAP HANA.
The 'powered by HANA' version is the way we know new capabilities are delivered to a BW on HANA release, the same way we have done this already with release BW 7.3. and BW 7.4. The 'edition for HANA' version however gives you the option to run a BW 7.5 on HANA system only with new and optimized SAP HANA objects. This allows a simplified governance and faster time to market with new agile and flexible data modeling patterns.
BW 7.5, edition for HANA comes with a 'switch' that turns off the ability to create any old objects like InfoCubes or standard DSOs. That also means if you want to move to this version of BW 7.5 you have to migrate all your old legacy objects that you might have in your current BW on HANA system. BW 7.5, edition for HANA will be the default for any new BW on HANA implementations.
You can find more information in the latest BW Roadmap deck - http://scn.sap.com/docs/DOC-68339
This new version is in ramp up right now. The following link will take you to the official ramp-up page in SCN.
Are there any best practice of how to upgrade to BW 7.5?
Please see the following link for all information about upgrade, code split and further considerations for the upgrade and implementation.