Station_two writes: If you do find a suitable "competing product", please pass it on. Adobe couldn't care less.
There are many competing products however as always it is dependent on your application - We primarily use Photoshop for lens correction and while the contained algorithms are quite good, many other products contain similar algorithms and work equally as well. Even the Gimp can do the same with little tweaking (although we will not be moving to the Gimp). Photoshop is quite limited in other areas (3D modelling etc.) however for the price it is a useful tool providing we can purchase it outright and continue to be able to purchase updates, although if as you say we cannot do this, then its probably time to move to something else.