I misread the MacPro reference and went MacBook Pro.
However, a browse around the store is still worth it.
What level of video editing are you active in?
If you do not already have the Mac software to do this editing with, the iLife suite does not come on the MacPro line, you will need to purchase new editing software. As grim pointed out, all new software is being written to take advantage of the Intel processor and not the old G5 PPC line.
Of course, the older versions are still available from other sources.
If you are planning on using this machine to run Windows, to use your existing editing software, you should be aware that the G5 processor is not capable of running a virtual windows machine. Only the Intel processors can do that. There is a program called Virtual PC which will run Windows in Emulation but unless you like playing with a PII running at 160MHZ, I would not go there.
If this machine is just for "hobbying" with video and sound, then it will make a nice addition and will perform excellently but if your "hobby" is your bread and butter, considering this machine may not be a wise business move.
I have to admit though, it is a very good price.
P