I just manually updated to 2.3.5 on my rooted nexus s 4g, had to reroot the phone after the update, it did not wipe any data or apps. wireless hotspot tethering works much better after the update. Noticed 3g and 4g improvements, at times I get an extra bar for 3g and wifi. No 4g widget found.
This post was made after tethering to my updated phone. The tether did not work well before the update, I think the update has made signficant signal improvements for my phone. I have not tested the speaker phone or any other claimed fixes or improvements.
Just to prove wireless tethering still works after the update, here is an IP/ISP lookup I did:
Location not accurate? Try: Update IP Location IP Information: 66.87.xx.xxx
ISP: Sprint PCS
Organization: Sprint PCS
Connection: Dial-up
Services: None Detected
City: Brooklyn
Region: New York
Country: United States