The seamless site is really one of the best interfaces to worldwide DEM data that exists. I know, I've looked. But it does take some getting used to. The thing of it is there's tremendous power, flexibility and access to data there. So it can be overwhelming. If you can just find a basic path through to the files you want then you can follow that in the future and it should be fairly easy. The main thing is to determine what data type you need, which will depend on the applications available to you. I do strongly encourage buying Global Mapper if you are serious about using DEM's. It's pricey, but for the money I don't think you can buy any other app that better supports a variety of real-world raster and vector formats, including virtually every known DEM format and direct Terragen .ter export as well.
- Oshyan