I am happy too with the current way 5e deals with magic items, and I agree with [MENTION=17077]Falling Icicle[/MENTION] that stacking needs to default to "NOT", then leave it up to a HR if wanted to stack.
Otherwise, the only caveat I still have with the current rules, is that the "must be +1 before having additional properties" is still there... It's not really a rule per se, but rather an idea silently creeping into the rules.
Among the current magic items in the playtest, only 2 armors out of 6 have a + to AC, but 10 out of 14 weapons have a + to attack and damage (not counting the plain-and-simple +N armor/weapon in these numbers, nor situational +s).
Not only there is NO story reasons why a magic weapon should have a + (it could have, but it's not a must), since "superiorly crafted" doesn't necessarily mean "makes it easier to hit the target" but it can mean a variety of things. And of course there is NO balance reason either like there was in 3e, since there is no built-in assumption in the game about what amount of +s your PC must have from equipment at every level.
But having +s from weapons goes against the bounded accuracy. It's not a huge effect, but it's still +1 in a system that is supposed to be bounded to +10 over the course of the whole level range (+5 from capped ability scores, +5 from class level), and IMO that +10% becomes significant, especially since the majority of PCs will be probably in the range of +3/+6 for a long time, so that +1 becomes more like +20%.
I am not saying we shouldn't have any magic weapons with a +, I am just saying that still having the large majority of sample magic weapons in the book grant a +, is "out of tune" with the current bounded accudacy design and adds nothing to the game. The DM is always free to make what items she wants, but still the items in the DMG set a trend...
Also, IMHO those +1 armors and weapons are great to give to those players who want low-complexity PCs, because they are active all the time and will just be added to your basic stats in the character sheet. At the same time, you can give complex magic items to the other players. But if those complex magic items also have a +1, then they are always better, so you'll now have to give +2 weapons to the first kind of players, and now those bonuses starts to get bigger...