If you are using bash, there's a shorter version of the script that calls pbpaste and wc only once and uses less resources. How about using the following:

count=($(pbpaste | wc))
osascript -e "tell app \"System Events\" to display alert \"Character Count: ${count[2]}\nWord Count: ${count[1]}\nLine Count: ${count[0]}\""

By using an array, you call the commands once and save overhead.

Also, in the Maccast where I heard about this post, I forgot what you called osascript but the "osa" stands for Open Systems Architecture.

Finally, I have no problems with not using full path names. The commands used are standard commands in the standard locations that are set by the default PATH variable.

Good luck!