Most of the Las weapons still use the standard FireSound method, so I doubt that's an issue. I've compared it to several other weapons and they seem to be working OK in terms of sound + effects.
What I'm noticing, especially with the Lascannon, is that it can sometimes fail to fire -- and then upon firing another shot, it'll process both shots as intended. The firing sound usually only seems to occur on the first shot of a given magazine or after waiting a short time between shots.
The Brotherhood of Nod seems to be having similar issues with its laser and tiberium flechette weapons (although the GDI's Merlin seems unaffected, oddly).
One constant between all of these is that they have very glow-heavy effects involved.
That said, the Imperium Plasma weapons - which are another set of fairly rapid-fire, glow-heavy weapons - seem completely unaffected and work fine.
