I want to talk about the Modern Magic Unearthed Arcana. I've got two projects that are based around modern times: Faultline and Alliance. Faultline is going to be a sequel to overland set over 5,000 years into the future, so I'm not going to work on it until I get Overland finished. Alliance is a modern city being invaded by monsters, where an eccentric billionaire hires people to keep the magic away from the common public (and then other groups get involved and hijinks ensue).
Now, in the 3.5 days, Wizards released d20 Modern, using the D&D rules in a normal setting. I loved the game and its "road to a hero" design. Characters had to start with one of the basic classes, which are generic classes with talent trees. They had to multiclass into Advanced Classes, which are more like the D&D classes. Alliance was built more from the d20 Modern idea of normal people slowly trying to understand the supernatural world around them.
The current d20 Modern articles we're getting for 5e is a "D&D in the present day" rules. I like them, but I don't think I'll use the class options for Alliance. Use the spells for Alliance, yes. Use the options for Faultline, yes. I can't see having a 1st level mage or warlock in Alliance.
I want to use the class options, but that's what Faultline is for. With some of these articles, they could try to make a d20 Modern book for 5e D&D. If they do, I want them to have both the "D&D in the present" as much as "Normal world invaded by magic." I think they're going to need some more magic-less, psionic-less, classes to pull it off, though. On the other hand, I don't think they're going to make a d20 Modern book until they work out the kinks with psionics.
Then again, I could use the Steve Jobs method and wait until people start releasing their own modern ruleset and then see what I can use and what I can improve on.