Speeds on Steam can slow down depending on traffic on their servers. I find it best to start something downloading when I go to bed, and usually it's done by the time I wake up. Then again, I think my ISP limits download speeds at certain times/hours of the day too.
I dont think that my ISP limits download speeds, but Steam is always very slow when downloading something. I might redownload it just so I can use it with Steam and get the achievements, etc. But I wish you could just activate it on Steam with a code that comes with your DC Universe account.
All times are (GMT -06:00) Central Time (US & Canada). Current time is 10:02:48 AM