Beefed up as in more RAM (a lot more it seems), not sure about the CPU, but I am going to say that it is also much faster with 80% certainty.... Also has a gigabit port, which, well, has no real point IMO unless you hit some kind of local cache on it. There is also potential for it to act as a print server or a type of NAS in the far future... Though I have doubts about that... Still wish I knew what the USB port was for.
As for the weight, I honestly think it's lighter than the 1000, but from pictures it looks like the coax cable is lower, so not as much stress is on the modem?