Formerly known as the Gripen NG (Next Generation) fighters, the JAS 39E is heavier (17 tons) that the existing 30C, has better electronics, a heavier payload (over four tons), and has a two seater version better able to handle ground attack and electronic warfare duties. The Swedish Air Force already has 134 JAS 39Cs in service and the prospect of more defense budget cuts made the purchase of 60 Gripen NGs (at a total cost of nearly $5 billion) seemingly impossible. But the JAS 39E excited several export customers and that made all the difference.
Sweden is describing the 39E as a "new aircraft" compared to the earlier JAS 39 models. There's some truth to that, as the 39E is a little longer and heavier but still looks like a Gripen. The 39E is full of more expensive, and capable, electronics, but that's not obvious by just looking at the new model. The first 39E is expected to fly this year and enter service in 2018.
The Gripen has already undergone one major enhancement to the JAS 39C model. Improvements included inflight refueling, better electronics, and improved ground attack capability. The C model was also compliant with NATO standards for warplanes. This was necessary for export sales. There was also a two seat D model for training.
The 14 ton JAS-39C is roughly comparable to the latest versions of the F-16. The Gripen is small but can carry up to 3.6 tons of weapons. With the increasing use of smart bombs this is adequate. Often regarded as an also-ran in the current crop of "modern jet fighters", the Swedish Gripen is proving to be more competition than the major players (the F-16, F-18, F-35, Eurofighter, Rafale, MiG-29, and Su-27) expected. Put simply, Gripen does a lot of little (but important) things right and costs about half as much (at about $35 million each) as its major competitors. More importantly, Gripen also costs about half as much, per flight hour, to operate. In effect, Gripen provides the ruggedness and low cost of Russian aircraft with the high quality and reliability of Western aircraft. For many nations this is an appealing combination. The Gripen is easy to use (both for pilots and ground crews) and capable of doing all jet fighter jobs (air defense, ground support, and reconnaissance) well enough.
The JAS 39 entered active service in 1997, and has had an uphill battle getting export sales. Sweden does not have the diplomatic clout of its major competitors, so they have to push quality and service. Swedish warplanes and products in general have an excellent reputation in both categories. Nevertheless, the Gripen is still expected to lose out on a lot of sales simply because politics took precedence over performance.