I updated my secondary MacBook Pro (15" Mid 2014) to Mojave on release day (I don't usually do this, but I heard a lot of positive feedback, so that encouraged me to upgrade). I did a clean install of macOS Mojave (completely erased the SSD). I noticed that Mojave is slightly slower than HS after few hours of use, I performed a SMC/NVRAM reset to rule out any issues caused by the SMC chip. Same results. So to be more objective in my judgment, I performed a clean installation of HS on my other MacBook Pro (15" Mid 2014, same specs), and compared them 1 to 1, and here are my results: - Mojave boot is definetely slower (the screen also goes black for a second or two during boot) - Performance wise, they perform almost the same, and where there was a difference in apps launch time, HS was faster. - MacBook Pro feels a little bit warmer under Mojave than HS, although indexing isn't running and laptop is sitting idle (close to 100% idle). - Battery life is slightly worse than HS, there's a 20-40 minutes difference depending on usage. - HS had some frame drops in UI transitions, Mojave didn't fix that and it suffers from the same issue (it isn't a big deal as it happens only occasionally). Other than performance, there are a few points I'd like to make. - Dark Mode is a joke. It looks and feels like it was hacked by an amateur UI designer on a weekend. They kept using the same icons from the light mode (they feel out of the place), the contrast is awful, and overall it doesn't fell like a professionally designed UI, especially by a huge company like Apple. - Even though both MacBooks have Retina displays, there is a slight difference in fonts/text between HS and Mojave (Mohave is slightly worse), text was bolder and more clear in HS. I'm not sure if it has something to do with AA being disabled in Mojave. Things I like about it: - Stacks, they're very useful. - Continuity Camera, this is brilliant! - New screenshots app, although I don't use it a lot but it's a nice touch. Overall, I think Mojave's UI wasn't polished enough, and Dark Mode isn't ready for release. If you're running a production machine and you're OK with HS, maybe you should wait until they fix these issues (although I don't think they'll change anything in the UI in any future Mojave updates).