Just installed DP1, and this is the fastest, smoothest, and most responsive Apple OS I've ever worked on. Every single animation is quick and buttery. Safari pages load instantaneously and without delay. Applications load at least twice as fast. Boot time seems to also be cut in half. I'm shocked at how good this update is! Currently running on a 2015 rMBP 15" w/ Radeon. EDIT: other examples of speed— Mail initially upgrading my database took one second versus the typical 20-30 seconds seen in past OS upgrades. The entire mail app is also 100% smooth and much faster. Photos opens instantly. There re no perceptible UI delays in this program anymore. Adobe CC launch times are also halved. All App Store pages load instantly. No more delays in this app.