SLR's servers are really weird.
When I had 500Mb I'd get average speeds of around 65% of my bandwidth. Then recently after I upgraded to 900Mb I was getting usually 50-75% used bandwidth from SLR. Then after I installed Internet Download Manager I now usually get 95% of used bandwidth.
The SLR speed test is just as weird, the results are all over the place, typically 150-250Mb download and 150-400Mb multi stream download. Current test right now from Birmingham UK to Falkenstein-7, DE is 77ms 260Mb for both at 18:25 on a Thursday, speedtest.net to the same town gives me 28ms 807Mb down. This is from Birmingham UK to Germany.
Almost all other websites servers are able to upload to me at max speed or close to it - without a download manager program. Before I got this program I very rarely experience any problems from SLR though! But this download manager certainly helps max out my bandwidth most of the time from SLR.
Streaming webcams hasn't really been an issue for me, barely noticeable at least. I've got a beefy spec'd PC so that might help.
Now 20 minutes later, just done another SLR speed test: 279ms 121Mb 193Mb to Falkenstein-8, DE.