I use them for two years. I bought the base supported my PR: O 15 in large rooms. Finally, I use most often it's because of the size, with two verses sub PR: O 18 Sub or Berhinger 1800X PRO.
There's may be a "hair" yield less compared to the PR: O 15 but nothing obvious.
I use a Yamaha P5000S amp or PS4800N and both QSC PLX 3602 (bi-amplification in 90% of cases).

Goodies:
- Size,
- Sound quality,
- Weight
- Ergonomics,
- Inclined base (avoids reverberations rather effective)
- Performance.

On the negative side, we could perhaps expect:
- Sound more detail in the midrange,
- A little more serious broadband

But for the price we already have a basic quality than enough for mobile disco applications (in large rooms up to 350 people with sub) or sound in a bar. For a group of musicos or benefit outside, we will say that it is not for ...

Question her, I had no negative feedback so far, on the contrary (for the record a person even told me: I know nothing about sound, but given the quality of the sound it must be good stuff .. or, "you've got a great sound, usually the sound is too rotten in this room ...).
on the other hand, for use with a quality amp and if sufficient attention to the case power ... even if, however, the PR: O 12 have more solid than air PR: O 15 on this map here.
Besides, if it again, I would have taken the PR: O 12 instead of 15 ...