Hi Steve,
No, it isn't 'too good to be true' - it is just 'a method', just like all the other processing methods that are available.
What you must understand are the implications of 'applying' the methid, and how the application of the method will affect your image data thereafter.
Using STF and HistogramTRansforms 'together' is what I do all the time - but ONLY because the 'alternative' is to use Histo only, and to constantly repeat a cycle of 'slider adjust' and 'apply process' steps to a preview of the image. Tweaking the sliders in STF, and seeing the result 'in real time' is far more intuitive, and certainly gets me 'closer' to the result I am after 'quicker'.
However, even after I have transferred the STF settings to the Histo process, I will stop and see what the Histo window is telling me - especially when it comes to the number of pixels being 'clipped'. Sometimes the most favourable results can involve passing the parameter setup back and forth between STF and Histo, before finally 'applying' the Histo Transform 'permanently'.
At least the two tools offer you various methods, and a lot of flexibility as well. In fact, the level of flexibility can often mean that there is little reason to resort to Curves to try and achieve the same results - which is something you could not say about other programs. (I usually only need to turn to Curves to tweak overall Saturation or to globally adjust colour, i.e. Hue)
As others have said, just be aware of 'how' a particular process is going to affect your image data, and keep your adjustments within your acceptable limits.
Finally, don't forget to 'zoom in' when you are making STF slider adjustments - and also consider stretching the STF window to the full width of your Monitor, both of which give you much finer control of the end result. Similarly, decide when you want the R, G and B sliders to be 'locked' to each other, and when to 'unlock' them - again, for much greater control (for example, when I make an initial 'AutoSTF', I try it both 'locked' and 'unlocked' - 'unlocked' can usually help balance severe colour cast issues right from the outset, although this is no substitute for a careful DBE, BackgroundNeutralisation and ColourCalibration sequence).
