I have a Series 0 running the GM. I have the workout enhancements, but I'm not using anything that calculates VO2 max, so I don't know if it tracks that.
The watch and the Health App on my phone have the new Heart Rate categories, but I'm not sure it's 100% of what you would expect out of a S2 or S3 device. I see my HR over the day, graphed out, with a range shown below. I also see a HR during exercise graph coinciding with the workout that I did yesterday. I have an empty space for resting HR, and Walking HR Average. I'm able to set a notification for Elevated HR, but not for irregular HR.