I love having the random treasure option back again. The treasure parcel system was giving me fits trying to plan adventures for my group, in which players drop in and out frequently, PCs may be of somewhat different levels, etc. Do I include an extra parcel or not, if over the course of gaining a level the size of the party changes? The parcel system is very fiddly.
In addition, if you're doing any kind of sandboxing, you don't want to preplan all your treasure placement. Now you could just keep a list of magic items in a queue to hand out, and even roll up the treasure as it's found, trusting to statistics (and perhaps occasional treasure audits) to keep the distribution in line over time.
This also goes for standard dungeon adventures (essentially a subset of sandboxing), in which PCs may run into more or fewer encounters than you had expected, changing the rate of level advancement, thus affecting whether you've planted enough parcels per level... blech! It can be done, but it's easier if you can just roll up a 2nd-level treasure instead of a 1st-level one if they get there before you expected.
Edit: Oh yeah, I also love the randomness!