No, I don't mean that the influx of new 90s in itself is a nightmare: it's the fact that now anything going wrong in LFR results in 10 minutes of bemoaning the boosted characters who are keeping everyone else from progressing. It's drama city out there. It's not that the moaning is entirely off-base: boosted players don't necessarily know how to play their boosted class at 90... but none of us were class experts as soon as we hit 90. And, come on, a random LFR group doesn't need boosted characters to mess things up and wipe.
So what's a player to do with this new LFR annoyance?
And boosted players? Your ilvl does let you immediately jump into LFR queues, but it doesn't necessarily mean you're ready for them. Be sure you take a the time you need to set up your button bars and pick talents and glyphs -- sometimes the best way to learn a class is by jumping in to the deep end, but be sure you're set up so you can swim rather than sink. Your boosted gear has a reasonable level but may not have the stats you need to succeed -- damage-dealing characters will especially find hit and expertise to be well below the caps needed to reliably hit bosses. Before queuing up, take the time to make the most of your gear, whether that's picking up some enchants or doing stat-shuffling with reforging to get your stats closer to where they need to be.
And, of course: have fun out there. That's what we're all here to do, after all.