I've never seen evidence of lag caused by them, although they do make invisible blocks which break multiblocks and some other things.
Really, people would check for the air ID? I've always used the isAir flag - seemed a lot more ... appropriate.They do create some lag, but only while forming the light blocks.
The lightblocks themselves used to be a problem, because no one's checknig for the isAir flag, and most simply check for the air ID, but neptunepink mitigated this problem somewhat by not letting the light blocks form 2 blocks from any solid block.
So yes, you could say they're "fixed" in that regard, although the problem never was on neptunes side to begin with.
They do create some lag, but only while forming the light blocks.
The lightblocks themselves used to be a problem, because no one's checknig for the isAir flag, and most simply check for the air ID, but neptunepink mitigated this problem somewhat by not letting the light blocks form 2 blocks from any solid block.
So yes, you could say they're "fixed" in that regard, although the problem never was on neptunes side to begin with.
Did Forge add the isAir flag? That would make sense for Vanilla to not use it, then. Or they always assume no one else is going to do something funky...Well, vanilla nether portal lighting and tree growth checks for ID=0 in 1.5.2 (I don't know if this is fixed by forge already in 1.6.2). Railcraft helps here a bit, by adding tracking aura which makes all those bugs more noticeable.
Did Forge add the isAir flag? That would make sense for Vanilla to not use it, then. Or they always assume no one else is going to do something funky...