I normally take negative reviews of a popular place with a grain of salt. Any restaurant that serves so many people is statistically bound to miss sometimes, and with so many different expectations/tastes, it is hard to please everyone. But this is a bit concerning the frequency with which these reviews happen.
While Ohana is very busy, this should not be a problem in itself. The nightmare for a restaurant/operations manager would be unpredictability -- trying to figure out how to staff, order perishables, and prep ingredients when your nightly menu and attendance are difficult to forecast.
Ohana has the blessing of being booked far in advance, operating near the same capacity virtually every day of the year (in both busy and slow seasons), with a limited set of identical menu items that most tables will be served. So for this restaurant, they should have being busy down to a science.
I don't know why people don't feel like they can ask a server to slow down the service, but if this is a source of dissatisfaction for enough people, one needs to look at the operation to see what's actually going on.