The Laser Rifle is a useful stopgap until plasma weapons are available.
Although it is inferior to the Light Plasma Rifle, the Laser Rifle is both faster to research and cheaper to produce.
The Laser Rifle becomes obsolete once you have scavenged or built enough Light Plasma Rifles to equip your entire squad.
While the listed Critical Damage in XCOM: Enemy Within is listed as 8-10, the actual values remain 7-9 due to a game bug.
Curiously, the EXALT Laser Rifle retains a detachable magazine of its conventional counterpart. This can be explained by reusing the familiar pattern for detachable batteries - or by the laser actually requiring single-use cartridges (not unlike the original gun), containing power cells and/or expendable laser media. An example of a laser that can operate that way is the deuterium fluoride laser.
When the Laser Rifle has been researched, a cut scene plays, depicting an XCOM scientist test-firing the weapon at a cardboard cut-out target using the "live Sectoid" image from the original UFO: Enemy Unknown/X-COM: UFO Defense.
When normally fired, it shoots a single laser beam. When used in Rifle Suppression, it lets numerous brief bursts. These are likely low-power blasts just powerful enough to keep the enemy at bay.
Unlike the other laser weapons, which have a grey paint, the Laser Rifle has a white paintcoat.