FS9, FSX The team who developed Topcat, the aircraft performance calculator, is also working on a new "professional" flight planner, the PFPX X. Several beta testers are now working on it and the final release date is expected this summer.
In comparison with current flight planners, PFPX X will include new interesting like cost index based flight plans and several features dedicated to long hauls (ETOPS/EROPS integration, NATS and PACOTS plans etc.). The graphic interface will be adjustable, the aircraft files will be editable. Of course, one of the strong points will be the easy interface with Topcat.
Here, some westbounds NATS tracks
More infos on the website.