I like to stock the plasma rifle and it's clips (which are really magazines) for a while and then distribute them to all of my bases, using them for base defence. I find them better for taking on Mutons and Ethereals rather than the Laser Rifle. Really accurate and powerful. Second only to the Heavy Plasma really. (Blaster Launcher doesn't count here)
I also use them to replace Laser Rifles ASAP until I can stock heavy plasmas. Even so, I still use them in my bases, which is fun enough
Overall, I believe they do most of the work in my bases. While my squad with flying and power armour takes on the next battleship, the rookies and squaddies in my ChinaCOM base take a knee and fire away at incoming Snakemen, Floaters, Mutons and Ethereals.
It's a good rifle. Not the best, but it's still good.
I kinda wish someone would make a Heavy Plasma rebalance so it's more in line with the rest of the "Heavy" rifles in the game. I really like the plasma rifle.