I've written stuff in shell over many years (I don't claim to be an expert, just average) but its not always smooth esp when I upgrade or change OS's. Most shell programs will make calls to other commands. These commands do not have standard arguments across unixes. Take the OSX (BSD) date and linux's date. On one machine I may have installed coreutils with default_names, on another without.

Sometimes, this forces us to make quick trips into perl or awk (to get yesterday or tomorrow). However, shell scripting has certainly made me more productive over the years. For most of my initial programming life (90's), I've generated boilerplate code using shell (often with awk).