Service Pack 2:

Service Pack 2 for Windows Vista was released to manufacturing on April 28, 2009, and released to Microsoft Download Center and Windows Update on May 26, 2009. In addition to a number of security and other fixes, a number of new features have been added. However, it did not include Internet Explorer 8:
Windows Search 4.0 (currently available for SP1 systems as a standalone update)
Feature Pack for Wireless adds support for Bluetooth 2.1
Windows Feature Pack for Storage enables the data recording onto Blu-ray media
Windows Connect Now (WCN) to simplify Wi-Fi configuration
Improved support for resuming with active Wi-Fi connections
Enables the exFAT file system to support UTC timestamps, which allows correct file synchronisation across time zones
Support for ICCD/CCID smart cards
Support for VIA 64-bit CPUs
Improves audio and video performance for streaming high-definition content
Improves Windows Media Center (WMC) in content protection for TV
Provides an improved power management policy that is up to 10% more efficient than the original in some configurations
Windows Vista and Windows Server 2008 share a single service pack binary, reflecting the fact that their code bases were joined with the release of Server 2008. Service Pack 2 is not a cumulative update meaning that Service Pack 1 must be installed first.

Platform Update:

The Platform Update for Windows Vista was released on October 27, 2009. It includes major new components that shipped with Windows 7, as well as updated runtime libraries. It requires Service Pack 2 of Windows Vista or Windows Server 2008 and is on Windows Update as a Recommended download.
The Platform Update allows application developers to target both Windows Vista and Windows 7. It consists of the following components:
Windows Graphics runtime: Direct2D, DirectWrite, Direct3D 11, DXGI 1.1, and WARP;
Updates to Windows Imaging Component;
Updates to XPS Print API, XPS Document API and XPS Rasterization Service;
Windows Automation API (updates to MSAA and UI Automation); (will also be available on Windows XP)
Windows Portable Devices Platform; (adds support for MTP over Bluetooth and MTP Device Services)
Windows Ribbon API;
Animation Manager Library.
Some updates will also be available as separate releases for both Windows XP and Windows Vista:
Windows Management Framework: Windows PowerShell 2.0, Windows Remote Management 2.0, BITS 4.0
Remote Desktop Connection 7.0 (RDP7) client;
Although extensive, the Platform Update does not bring Windows Vista to the level of features and performance offered by Windows 7. For example, even though DXGI 1.1 update introduces support for hardware 2D acceleration featured by WDDM 1.1 video drivers, only Direct2D and DirectWrite will employ it and GDI/GDI+ will continue to rely on software rendering. Also, even though Direct3D 11 runtime will be able to run on D3D9-class hardware and WDDM drivers using "feature levels" first introduced in Direct3D 10.1, Desktop Windows Manager has not been updated to use either Direct3D 10.1 or WARP software rasterizer.