I stayed at this hotel Wednesday night and was given a refurbished room on the 29th floor. Personally, I had no problem with the rooms the way that they were and didn't necessarily think that they needed refurbishment, but anyway...
The entryway has been redesigned and there is now a wood floor at the entry in place of carpet - it's nice. There is a new headboard on the bed with two small LED lights built in on each side (for a total of four) which can be controlled separately - perfect for reading in bed. The carpet has been replaced as has the furniture and desk.
In the bathroom, it didn't look like that much had been done, but the dual-head shower is gone and has been replaced by a rainfall-esque (not quite really rainfall, but getting there) shower head. I was surprised by that as I thought the dual showerheads were a Westin standard, but then again I didn't mind as I generally only use the one anyway.
The elevator lobby was also redone with new lighting, wallpaper, pictures, etc. Overall, the renovated room felt much fresher -- as other posters have mentioned, however, there is construction noise starting at 830 AM (I was warned of this issue before I agreed to take a room on the 29th floor).
This continues to be one of my favorite Westins due to the high number of junior suites and the blockbuster views. I also like the Sheraton Boston, but something about this Westin just makes me feel extremely comfortable when I'm there.