I assume you're talking about the pistol. Basically - I got complaints from the first demo that the pistol felt far too convenient relative to the other weapons. As a result people didn't feel a need to use anything else since the pistol has unlimited ammo AND is reasonably powerful.
The idea behind the change is that the pistol can be powerful and have (functionally) unlimited ammo (since it's an energy weapon anyway) - but it has to have some kind of drawback that makes it untenable to use all the time. I figure its current configuration makes it just inconsistent enough that the other weapons will become safer bets - and thus used more.
The level select thing is a good point though, actually.
