The pistol Shrimp isnt nessacarily the bad part. Digging isnt ussually what you want for your DSB if he goes to deep and disturbs your denitrification layer. But most Gobies will eat the infuana from your sandbed which you need to keep it clean and the biological process of the Sandbed going.
You can have one, but it would get expensive over time to replenish the DSB of critters that your gobie would be munching on.
Im sure you will hear people who say "Well ive never seen my Gobie take a bite out hte sandbed and Ive had him for years!"
But unless you watch your fish 24/7, you cant really prove that.
I will be removing my Pistol Shrmip and Gobie pair as soon as I can get ahold of them

He just rearranges my sandbed more than Id like and I only see him once in a great while. The Pistol Shrimp is Blind therefore he seeks the protection of his cave at most times of the day and relies on the gobie to keep watch on their burrow.
Great pair for a small Nano Tank in my opinion, but I wouldn't do it again if I had to start over with my tank.
Just my Opinion
Joe