I bought the game release day (never pre-order games even with they hype this was generating) and have played it for 16 hours according to steam. At this time my city is about 39,000 population and I've bought 5 expanding squares but I chose the island map so i got less land to play with. There are numerous great things about it and a couple annoying, easy to fix things that I'm sure modders or the devs themselves will fix.
Public Transport is currently a nightmare. The only way to differentiate between bus lines is to find a bus and click on it to change the line color so you can actually see where the line goes. You can't do this for metro and trains and if you edit your roads after you make bus lines the lines become so chaotic you will probably just have to remake them from scratch. Also buses can cause inordinate amounts of traffic if this happens.
Traffic AI is literally aids. They will no matter what take the shortest route from a to b even if it means they will end up on non-arterial roads. They also will stay in the right hand lane 90% of the time no matter the amount of cars, even with a 4 lane one way road. The amount of traffic in relation to population seems to be extremely unbalanced as well, even with amazing road planning. god i hate transportation.
Crime is currently a non-issue in the game as it never goes above 8% as long as you keep happiness high, so there is really no need for alot of police stations. Hopefully they will adjust the crime algorithm soon so that it actually has impact.
Alot of things are not readily explained or easy to deduce, such as the need for uneducated workers in industrial zones. The only way to get these is to do the opposite of what is logical which is to build houses with low land value near these zones, otherwise the industry abandons buildings non stop. This is an extremely realistic feature but is counter intuitive.
Performance wise the game runs fairly well and looks good considering the amount of stuff you can see on the screen and interact with (you can literally follow every single person to every single place) but with larger cities like mine is becoming the frames do drop a bit to below 60 sometimes. I haven't looked at my gpu performance with the game running but I can definitely hear it sometimes (twin frozr 7970 amd fx8350)
I also played a ton of SC4 as a kid and this game is the next best thing. All it is missing is giant death robots and volcanoes to be a true recreation of SC4. Skylines does not have the inter-city relationships like sc4 did though, which would honestly make it a 10/10 for me if it did. I disagree with KrocketKarma as city sims have nearly infinite replayability with making maps and adjusting your city to new landscapes. There are already people recreating cities in 1 to 1 scale from the real world and with mod support day one this game will be amazing years from now. Also they have end game buildings with tons of different pre-requisites that would take hours to get.
TL;DR Good game with mods and a few easily fixed issues. Brings back memories of the good old days in SC4
sorry for the long post but I've had a couple friends message me about the game and felt I should just post the best thing i could where most of them could read it