I've worked several 2,000 mile stations (on 20 meters) in the state of Washington recently.
I worked KE7PZX (twice) in the last 10 days and also worked WC7C. (in Washington). Some of the other stations I've worked have been in Texas and Florida. (W5VYN--W5GXV & K3RLL). I also worked VE9CQ in New Brunswick and VE1BA in Nova Scotia. All of which are at the 1,000 mile range using my QRP rig and the indoor Isotron antenna.
But I don't spend a lot of time on 20 meters because I find most of these contacts are very weak, and only allow the basic exchange of signal strength, name, and location. The CW speed is also seldom less than 15 wpm. (Most are at 25+ wpm and a little too quick for me).
I've worked 34 DX stations now with my QRP rig and simple wire antennas. Several have been at 4,000 miles (or more) but I only remember one station (in Germany) that took a few minutes to actually 'chat' with me. It was a 10 minute QSO and an extremely rare instance. I find it amusing when I make long distance contacts, (yes I enjoy them from time to time) but they're not the very "best". I guess there's different things for different people, but still, my biggest joy is making a contact with another QRP operator.
When I worked K3RLL, (QRP) in Daytona Beach Florida, his batteries were about to go. But I still made the contact as he used a little QRP rig and a simple wire antenna while operating from a city park. My contact in Nova Scotia (VE1BA) was also QRP but using a small beam.
As I look over my log book now, I see a little over 800 contacts. Of those, 182 stations have been North American QRP CW Club (NAQCC) members.
Those QRP CW contacts are what I would call my "best QSO's".