I have the 3. So far, so good. The suction mouth is a bit big IMO but nothing you can't get used to. I used the DM2 for a long time so that's what I was used to. They are about the same size and function similarly. I cleaned a sofa and Loveseat with the DM3 this morning and thought my valve was leaking a little but couldn't pinpoint it. It cleans really well (DM2 did too.)
The major thing
HydraMaster addressed was those stupid metal lips on the DM2. I actually have the DM2 with a brand new (not installed yet) head and lip kit that I'd sell for a decent price if anyone's interested. IMO the head with the metal lips is trouble, it's just a matter of time. I have thought about installing the kit but putting super glue or something between the metal lips and plastic head to prevent problems.
I've been pretty happy with my DM3. I like new toys too, I kinda wish I had one of those Sapphires everyone is always raving about...I'd probably have to get one of those bags Jim Martin was showing off too.
The Clean Machine