As announced on the official Second Life blog, the Voice feature is now integrated into the main SL client. Voice is one of the new features I have been eagerly awaiting since having experienced a taste in the beta testing phase way back in March.
1. It will speed up many content creation activities; specifically the process of building (typing and building at the same time is difficult)
2. Communication with people who speak foreign languages will be easier (for example, Its easier to understand spoken Japanese than written Japanese)
3. Those who's typing speed is slow or who are dyslexic will be able to participate in discussions to a greater extent
4. I believe it will increase immersiveness
To prove my point about increased immersion try out the Holophonic exercise below (requires headphones):