said by qworster 
:said by RARPSL :said by sibisties :You forgot to mention the incredible upload speed for these tiers... It's an incredible 1Mbps !
That upload speed is a farce. With the 50Mbs (and possibly the 30Mbs) tier, I do not think that you can get the full download speed with only a 1Mbs Uplink speed (you need to send too many ACKs and will saturate the uplink). There is also the problem that even if the uplink can handle the volume, the speed will bog down due to not sending the needed "Send More" ACKs fast enough.
You are correct. For optimum results, the assymetry between download and upload speeds should not exceed 10:1.
With these it will be 30:1 and 50:1.
Of course the Sliding Window and especially SACK (Selective ACT) helps reduce the size of the Upload Stream but nothing overcomes a slow upload speed since you have to deliver the "I got all the packets up to this packet number - Keep Sending Packets" Handshake Responses and if the do not arrive and get processed before the buffer empties you will not get the full download speed. I do not know the bits-and-bytes internals but as you agreed I do not feel that a 1Mbs uplink can support a full blown 50Mbs (or probably 30Mbs) downlink. 
