No worries, it's just that it's a weird problem, thus all steps should be tried, because you never know what may be causing it. But if ping and traceroute respond with shitty times, then it's not browser related.
The only other thing I may suggest trying is toggling IPv6 support, though I doubt that has anything to do with it. I know I'm without IPv6 and I don't have troubles downloading, not sure how your installation is set up. I'd say your best bet is to call your ISP though.

But who knows, maybe someone else has another suggestion.

I've been noticing some very slow GOG download speeds as well. I used to be able to download at least 1 MB/sec, and now it's barely 100 kb/sec through both ways. I did a speedtest on my own connection and it said it was fine. I also did a ping to that "Edgecast" site and it was less than 60 ms which isn't too bad. Do the GOG devs know why the speeds are getting slow for a lot of people? Trying to download a GOG game that's over 1 GB in size through a download speed of only 100 kb/sec is far too slow.

As for the OP did you try using both downloader and browser option?. Try another browser?. Disabled addons or extensions etc?

Yep. I tried all that and the download speed is still incredibly slow. It's barely 100KB/sec. :( Is there anything else that can be done to fix this?

I dont see how its a major problem - you and Crosmando are the only ones ive seen complain about slow speed over the last few days (i frequent the forums often). Im downloading a few games right now and its maxing out my adsl2 connection (17mb line) - i havent had any issues so i honestly dont know. Have u spoken with support?

I just sent a message to support, but I'm still waiting for a response. I really hope this can be fixed. I've tested my connection speed to other websites and it says the connection is fine. I just don't understand why it's only GOG that's giving me a slow download speed.

Same thing happening here - download speed of around 34 kbs :( Every other site gives me normal (fast) download speeds. I won't put in a ticket yet until I hear what they say to you in case one answer fits all!