Yes, I am prepping for a July 18 day hike. Some friends scoff at my preparations but I have read books, read forums, taken notes, talked to past hikers, make a day trip to the portal a couple weeks ago to hike up to Lone Pine lake during daylight hours, even used google earth to 'fly over' the Halfmile maps of the trail. I know this is one mountain to give much respect. The tragedy of Mr Likely punctuated that.
Glad you're not listening to your friends. Whitney is a serious mountain that is often under-estimated because "you can simply walk to the top", without any scrambling or technical climbing. Every so often, though, a tragedy like John's provides a sobering realization that, yes, there can be very real dangers here, regardless of your skill level. Preparation is the majority of the battle to getting up and down safely. The rest is really just paying attention and using common sense.
Assuming you're conditioned, acclimated, and geared up properly, the biggest challenge you'll likely face in mid-July is weather. Expect anything and everything due to potential monsoon conditions that often come that time of year. Last year we were blown off a summit attempt the third week of July by some of the worst weather I've ever seen outside a hurricane or tornado - torrential rain, snow, hail, graupel, high winds, lightning, rockfall galore - it was mucho ugly. But I've also been up in mid-July when conditions were absolutely perfect and wore only stripped convertibles and a base tee on the summit.
This tragedy, as you said, punctuates a potential danger. Watch for those lefts descending to ML and you'll be fine.
