One point of correction: It is definitely possible to see current, instant results in Google Analytics. Just click the drop down menu in the upper right and change the time period to include the present day. By default it shows the last month, not including the present day, but you can adjust the time period to show just results from today, for example.
So many people do not realize this and then say that you have to wait a day before seeing any stats in Google Analytics. On the contrary you definitely can see instant results, the interface just doesn't make this as easy as it should be.
That really depends on the traffic your site is getting. If it's a decently large site (> 50k PVs a day), then yes, data for the current day will be lagged. But for most sites smaller than that, I've found the data to be only lagged by 15 minutes or so. It's definitely improved over the past year.
Can't speak to that, I don't pay close attention to daily stats for my personal site, and all the sites I work with are big enough to have a heavy delay.
So many people do not realize this and then say that you have to wait a day before seeing any stats in Google Analytics. On the contrary you definitely can see instant results, the interface just doesn't make this as easy as it should be.