Here's the 2013 rendition of the cosmological Mona Lisa,
or, in our jargon, the multipole expansion of the Cosmic Microwave Background (CMB) power spectrum. Compared to previous experiments, what distinguishes Planck is that it measures the power spectrum all the way from the largest angular scales down to less than 0.1 degrees. Before, to cover the entire range, one had to combine several different CMB experiments: WMAP, SPT, ACT, which was more vulnerable to unknown systematic errors (indeed, the results from SPT and ACT were not completely consistent). Thanks to Planck, the errors are reduced, especially at large multipoles, and the confidence in the results is strengthened.
For the general public, the most palatable piece of information is about the composition of the Universe. The dough is made of 69.2±1.0% dark energy, 25.8±0.4% dark matter, and 4.82±0.05% baryons, after combining Planck with other cosmological measurements. As you can see, the errors are of order 1 in 100, which represents a factor of 2 increase in precision compared to WMAP-9. The central values have shifted a bit: there's additional 2% of dark matter at the expense of dark energy, but the change is consistent within 2 sigma with previously quoted errors.
From a particle physicist's point of view the single most interesting observable from Planck is the notorious Neff. This observable measures the effective number of degrees of freedom with sub-eV mass that coexisted with the photons in the plasma at the time when the CMB was formed (see e.g. my older post for more explanations). The standard model predicts Neff≈3, corresponding to the 3 active neutrinos. Some models beyond the standard model featuring sterile neutrinos, dark photons, or axions could lead to Neff > 3, not necessarily an integer. For a long time various experimental groups have claimed Neff much larger than 3, but with an error too large to blow the trumpets. Planck was supposed to sweep the floor and it did. They find Neff=3.3±0.5, that is no hint of anything interesting going on. The gurgling sound you hear behind the wall is probably your colleague working on sterile neutrinos committing a ritual suicide.
Another number of interest for particle theorists is the sum of neutrino masses. Recall that oscillation experiments tell us only about the mass differences, whereas the absolute neutrino mass scale is still unknown. Neutrino masses larger than 0.1 eV would produce an observable imprint into the CMB. In fact, the SPT experiment recently made a claim that the sum of neutrino masses is 0.32±0.11 eV, a 3 sigma evidence for a non-zero value. That would be huge, if confirmed. Well, no such luck:
Planck sees no hint of neutrino masses and puts the 95% CL limit at 0.23 eV. (Check out the comment section for a more informed statement).
Literally, the most valuable Planck result is the measurement of the spectral index ns, as it may tip the scale for the Nobel committee to finally hand out the prize for inflation. Simplest models of inflation (e.g., a scalar field φ with a φ^n potential slowly changing it vacuum expectation value) predicts the spectrum of primordial density fluctuations that is adiabatic (the same in all components) and Gaussian (full information is contained in the 2-point correlation function). Much as previous CMB experiments, Planck does not see any departures from that hypothesis. A more quantitative prediction of simple inflationary models is that the primordial spectrum of fluctuations is almost but not exactly scale-invariant. More precisely, the spectrum is of the form P∼(k/k0)^(ns-1), with ns close to but typically slightly smaller than 1, the size of ns-1 being dependent on how quickly (i.e. how slowly) the inflaton field rolls down its potential. The previous result from WMAP-9 ns=0.972±0.013 (ns=0.9608±0.0080 after combining with other cosmological observables) was already a strong hint of a red-tilted spectrum. The Planck result ns=0.9603±0.0073 (ns=0.9608±0.0054 after combination) pushes the departure of ns-1 from zero past the magic 5 sigma significance. This number can of course also be fitted in more complicated models or in alternatives to inflation, but it is nevertheless a strong support for the most trivial version of inflation.
I was a bit surprised by how much emphasis in today's press conferences was put on the small glitches at low multipoles. It seems that Planck people are also a bit frustrated by the fact that their results are nothing but a triumphant confirmation of old paradigms. Even at the LHC nobody would make a big deal of a 2.5 sigma anomaly, and in the present case we're in the area of astrophysics where error bars are treated more loosely ;-) Moreover, according to Planck, the quadrupole mode in the fluctuation spectrum is aligned with the ecliptic plane, which suggests some unknown background or pesky systematics at large angular scales. Of course, many a theorist will come up with a beautiful explanation of the low multipole anomaly. But not because it's convincing, but because there's nothing else to ponder on...
In summary, the cosmological results from Planck are really impressive. We're looking into a pretty wide range of complex physical phenomena occurring billions of years ago. And, at the end of the day, we're getting a perfect description with a fairly simple model. If this is not a moment to exclaim "science works bitches", nothing is. Particle physicists, however, can find little inspiration in the Planck results. For us, what Planck has observed is by no means an almost perfect universe... it's the perfectly boring universe.
Mind that this post is an outsider's perspective from the angle of particle physics. For a better insight into cosmological aspects of the Planck results see for example here. Note that Planck dumped 28 full-grown papers today, so browsing through it will take some time, and there may be some hidden treasures at the bottom of the chest...