I am some what reluctant to jump into this discussion, but since the merits of signature reduction have been raised I thought I would add this.
RF “stealth” does not make an aircraft “invisible” and it never has. What signature reduction does is to make an aircraft more difficult to detect in a given frequency range. In the air-to-air arena the radars are generally in the X to Ka-bands because of the need for a smaller antenna to fit on a fighter aircraft (leaving out AWACS for the time being). These bands require a set of materials and shaping which is characterized by the F-22.
In the air-to-ground arena these higher frequency bands are associated with mobile SAM radars for same size reason in that they are easy to move around and have very good range resolution. This is where the F-117 was optimized and where the F-22 is also fairly good.
Now you also have the lower frequency bands associated with the long range, high power, search radars which feed cueing information to the shooters and allow them to be more effective by only have to look at a particular sector of their firing area. These lower frequency bands require a set of materials and shaping which is characterized by the B-2. The F-22/F-35 are not that good in this arena. And most operational tests against SAM systems assume a cued system giving the shooters the best chance for an engagement.
Then there is the issue of IR detection which can be reduced in the mid-wave with materials as the detected energy is primarily reflected energy. However signature reduction is very difficult to do in the long wave where skin heating is the primary source of the energy detected. As a target, the only good news is the IRST systems do not track in range but only in azimuth. While there are ways of passive ranging a target they mostly rely on a non-maneuvering target.
The conclusion is that for every aircraft a decision must be made as to whether the cost of signature reduction and the advantage it creates in the combat arena are worth the cost in design and maintenance. RF signature reduction in air-to-air still reduces the range at which most fighters can detect and range on a target. For some manufactures, however, the advantage of stealth has been over stated.