I would argue that they did not clearly inform their customers. I found out about this through a post on Engadget, which led me to the Netflix blog. For a change as significant as this they should have emailed every customer. Unless they send out an email between now and then, I'll bet a large percentage of Netflix subscribers won't "discover" this change until they are suddenly billed 20% to 50% more in September.
I think the throttling thing was a long time ago. I've been a Netflix subscriber for 4 years and have never been throttled. And yes, there have been many occasions where I've sent discs back on the same day I received them (putting them in a blue mail box that hasn't been picked up yet). The only delays I've ever had were due to postal holidays or once when a couple of discs over a span of a few days were mangled in some processing equipment (the USPS dutifully delivered the torn-off front flap to me, sans DVD).