I like to enjoy the individual character of a particular film, as to me this is one of the features of film photography. Stand developing tends to reduce the contrast, so the results aren't the same as if developing to the manufacturer's spec, or perhaps using different developers to bring out certain characteristics. Where possible (due to light conditions, etc.) I like to choose my film to suit the subject and mood I want to capture, using the characteristics of the film (grain, contrast, sharpness, etc.) to do this (hopefully!).
I don't enjoy faffing with Photoshop or Lightroom, so getting it as right as I can 'in camera' is my preferred option for film photography, that way I get to appreciate the character of the film as well as a sense of achievement. As Simon says, there's nothing that looks quite as nice as a properly developed film that's turned out 'spot on', plus you know you've nailed the exposure as well as the development.
Hope my thinking makes sense to you. Best of luck with the experimentation though, but perhaps try to avoid changing ISO half way through a roll, unless it's something like XP2 which allows for some leeway if the light is right (in sunny conditions XP2 looks very good shot at 200 ISO and developed as standard 400, but then again, XP2 is a C41 process film and not standard B&W).
If you do, what's the betting the frame you've cut right through the middle of is the best one on the roll!