[en] RHIC introduced the method of hard scattering of partons as an in-situ probe of the the medium produced in A+A collisions. A suppression, R_A_A ≈ 0.2 relative to binaryscaling, was discovered for π"0 production in the range 5 < p_T < 20 GeV/c in central Au+Au collisions at = 200 GeV, and surprisingly also for single-electrons from the decay of heavy quarks. Both these results have been confirmed in Pb+Pb collisions at the LHC at = 2.76 TeV. Interestingly, in this p_T range the LHC results for pions nearly overlap the RHIC results. Thus, due to the flatter spectrum, the energy loss in the medium at LHC in this p_T range must be ∼ 40% larger than at RHIC. Unique at the LHC are the beautiful measurements of the fractional transverse momentum imbalance of di-jets in Pb+Pb collisions. At the Utrecht meeting in 2011, I corrected for the fractional imbalance of di-jets with the same cuts in p-p collisions and showed that the relative fractional jet imbalance in Pb+Pb/p-p is ≈ 15% for jets with 120 ≤ ≤ 360 GeV/c. CMS later confirmed this much smaller imbalance compared to the same quantity derived from two-particle correlations of di-jet fragments at RHIC corresponding to jet ≈ 10 - 20 GeV/c, which appear to show a much larger fractional jet imbalance ≈ 45% in this lower range. The variation of apparent energy loss in the medium as a function of both p_T and is striking and presents a challenge to both theory and experiment for improved understanding. There are many other such unresolved issues, for instance, the absence of evidence for a effect, due to momentum transferred to the medium by outgoing partons, which would widen the away-side di-jet and di-hadron correlations in a similar fashion as the k_T-effect. Another issue well known from experiments at the CERN ISR, SpS and SpS collider is that parton-parton hard-collisions make negligible contribution to multiplicity or transverse energy production in p-p collisions-soft particles, with p_T ≤ 2 GeV/c, predominate. Thus an apparent hard scattering component for A+A multiplicity distributions based on a popular formula, dN"A"A_c_h/dη = [(1 - x) (N_p_a_r_t) dN"p"p_c_h/dη/2 + x (N_c_o_l_l)dN"p"p_c_h/dη], seems to be an unphysical way to understand the deviation from N_p_a_r_t scaling. Based on recent p-p and d+A measurements, a more physical way is presented along with several other stimulating results and ideas from recent d+Au (p+Pb) measurements