Thanks for the feedback! :D
Yeah the spawning code is very similar to the random spawning code used in the Glitch Garden section of the Unity 1 course. I've got a minimum and mean time to spawn and a maximum number of spawns at any time. Every 5 successful spawns causes an increase to the travel speed but doesn't change the spawn rate essentially it ramps up the difficulty by moving the objects by quicker and having them show up less often.
The code for this is in /Assets/Scripts/BottomScroller.cs if you wish to check it out.