There are some pretty outstanding times there. My usual routine is to do 5k which takes me 20 minutes on the erg. Nearly broke the 20 minute barrier but I'm on 20.06 at the moment.
500m I can do it in 1.36 but wouldn't like to try 2.5k at that pace.
It's great but Erging can be torture when you're really going for it..
Anyone who wants to take up rowing it's one of the best forms of cardio out there. After trying one out at the gym I bought a model D Concept 2 with a PM3 monitor in October 2008 and have never looked back. Off Ebay, it was the best £650 I've ever spent and it won't take long to give me the payback against gym fees. It's nice to play some counterstrike source for an hour or so and then decide to go for a row.

Don't ask me what I wear for the rowing though....
If you cross train with other activities you're also going to get into great shape. I combine erging with freestyle lap swimming at my local uni pool and cycling when the weather is half decent. I'm thinking about taking up jogging in the spring too.
Especially if you're overweight erging is low impact (as said above, read up on technique or get someone who knows what they are doing to watch you) activity and the weight will fall off if you combine it with the right foods.
Check out Cracknell and Pinsent in this vid to see a superb race.
Erg on!
Also, a good rowing technique vid is this one. I found it to be very useful