was it constant all the time?
It was constant at around 400KB/s when I was making that download. But in general is not constant. At off peak hours I can get very good speeds but at peak hours it sucks. Now it is noon on Saturday and I get good speeds.

But also I noticed it depends on how I download. If I download somehting from a torrent then I get very high speeds. If I try to watch a movie from youtube for example is not good. I don't know... I guess they are testing things.
This is what I think they are doing: They gave to some people higher speeds. They are testing with giving 2.5Mbit or even 5Mbit. At not peak hours these people can use the maximum of their speed. At peak hours there is not enough bandwidth for all of us so the speeds suck.