Great topic! Nice to see some intellectual debating... Here's some thoughts:
Evolution doesn't cause adaptation. Adaptation happens randomly (via mutations and genetic variability due to crossover if I recall correctly), and the environment selects for or against these adaptations through various pressures (i.e. climate). 'Successful' adaptations will increase in proportion/allele frequency, and therefore the species has evolved. A couple of unusual mutants does not constitute evolution (though it may be in the process of occurring), but when those mutants have taken over, it has definitely occurred. At what point it could be said to have taken place is pretty grey, as are lots of things in this area. Nature doesn't like to follow human definitions and categories:-)
Evolution is generally considered to happen gradually, and over long time scales. There are some examples, however, of things which seem to have evolved very rapidly, with sudden jumps instead of baby steps. Keep in mind, though, that on an evolutionary scale, 'rapid' is still a very long time.
I don't believe that the 'basicness' of an organism's genome has anything to do with it's rate of evolution. Bacteria, virii, etc. evolve quickly because they have incredibly short generation times. Therefore, mutations which are selected for can reach large proportions of the population very quickly, at least with our human sense of time.
Mudskippers are fish:-) They just behave like amphibians...