I have installed 2 different brands and am aware of another 2.
In my own home, we installed film on just some panes in a Ranch Slider, with the rest either left clear, or with standard window film applied.
My observation is that very often, we get condensation on the panes with Low-E film only. This is a concern, as traditionally, window film does not like excessive condensation. Over time, the film's scratch resistant coating deteriorates and becomes almost obscure.
The second thing with condensation on the film is a big loss in performance of the Low-E coating. In effect, at the time you want the performance of the Low-E most, the film reduces only a small amount of heat retention. Remember, the main benefit this film type is marketed for, is to keep your house warm.
Given the huge price this film commands, is it worth it? I would just fit standard solar control film to block UV and keep the house cooler in summer. This addresses the other 2 benefits Low-E film is promoted for. Essentially, you can get much better performance at a much lower cost.
We have also experienced significant installation problems, which may only show over time.
An example is here: