It is already possible to get an indication of how well SQL Server 2008 will perform before it is released as there already some TPC benchmarks published for it. The performance of Integration Services has been separately tested, as have a number of applications such as Microsoft Dynamics and SAP. The links to all of the tests can be found here
These figures should improve slightly as all of the code is cleaned up closer to release, but this work has been possible because of the very different way that SQL Server 2008 was developed. Each feature was only included in a given CTP when it was pretty much working. This has also made early adoption a lot less painful as by and large a feature has remained unchanged once it was included in a CTP.
Of course your applications are all different and although benchmarks try and emulate the real world, they are no more than indicators like 0-60mph times for cars
. So try the latest SQL Server 2008 CTP on your applications and see what it does for you.