I'll have a full write-up later today, but if you've been itching to get your hands on Windows Vista Service Pack 1 (SP1), it's available now from the Microsoft Download Center in 32-bit (x86) and 64-bit (x64) variants:

Brief Description
Windows Vista Service Pack 1 is an update to Windows Vista that addresses key feedback from our customers. SP1 addresses specific reliability and performance issues, supports new types of hardware, and adds support for several emerging standards.

Overview
Windows Vista Service Pack 1 (SP1) is an update to Windows Vista that addresses feedback from our customers. In addition to previously released updates, SP1 will contain changes focused on addressing specific reliability, performance, and compatibility issues; supporting new types of hardware; and adding support for several emerging standards. SP1 also will continue to make it easier for IT administrators to deploy and manage Windows Vista. Windows Vista Service Pack 1 Five Language Standalone version can be installed on systems with any of the following language versions: English (US), French, German, Japanese, or Spanish (Traditional).

Read the overview of Windows Vista SP1, including what's new, technical details, guidelines and notable changes.

Read the Deployment Guide for Windows Vista SP1. This guide includes technical information, procedures, and recommendations for installing Windows Vista SP1 in a business or corporate environment.

DO NOT CLICK DOWNLOAD IF YOU ARE UPDATING JUST ONE COMPUTER: A smaller, more appropriate download is available on Windows Update.

Looks like the x86 version is 434.5 MB, while the x64 version is 762.5 MB.