Alright, I did a little research to follow up on my own question, and I've just been very impressed by Netflix.
I went to the "help" section of their site, and it immediately posts their phone number for customer service -- open 24 hours a day, 7 days a week. That alone was rather amazing, as a service like Netflix wouldn't seem to be something that required blanket customer service, but they're providing it anyway. I called them up, and there was no menu. No "Press 1 for this, Press 2 for that, press 76 to return." It just immediately attempted to connect me to a Netflix representative. I was on hold for 30 seconds or so before they were available. Also fantastic.
Once I was talking to the representative, I was told that Netflix updates their movies on Tuesdays, but those updates should be shown on the website on Sunday Evenings. In regards to the Watch Instantly queue, there are occasional weeks when there is nothing added -- if they just aren't able to acquire new licenses -- and other weeks where 10 or more movies are added, along with TV shows. It's not a consistent amount, it's just whatever they can manage to acquire the license to, as they're constantly fishing for more movies to add.
He then referred me to this website:
www.hackingnetflix.com
Which is a third party site but Netflix feels is very well run and keeps great tabs on what Netflix is doing. They are apparently very positive about it and encourage customers to investigate how their stuff works and what is coming up, like this website owner does. Best customer service I've had in a long while.