Compared to previous games in the series, SimCity is a bit different, for one thing, power & water are carried along roads, which removes the need for water pipes and powerlines, and you can just have roads. Normally I'd object, but with the way this new SimCity works, and the fact that the area you can build in is smaller than previous games in the series, it definitely is the better choice. Also zoning and any other building can only be done along roads, this is just another effort to simplify things, and it doesn't affect gameplay too much, as nearly all (if not all) buildings needed roads to them in order to operate in previous games, not to mention it really is more realistic.
The Glassbox engine is a great improvement, when it works... Now, instead of traffic etc. just showing a visual representation of a simulation, like in SimCity 3, how traffic would appear in busy areas, but disappear when they got to less busy areas, as the traffic weren't actually real, they were just there to show that road was busy. In SimCity 5 however, traffic are there, each one is persistent throughout your town, they'll leave houses, drive to work, and drive back to their house when work ends. This greatly improves the realism of SimCity, as times between 6AM-9AM and 4PM-8PM tend to get really busy, due to work/school starting/ending. Emergency vehicles also have to get to the location of the emergency in order to deal with it, instead of you just placing a firepole thingie there and it being dealt with almost immediately. Because of this, it's important to keep congestion down, otherwise your emergency vehicles will get stuck in traffic and the emergency could easily get out of hand. There are currently issues with the traffic AI, which is being addressed in the next patch, this includes traffic AI choosing a less busy route if one is available, instead of just whatever is the shortest route, like they do now, and also giving priority to emergency/service vehicles at junctions.
You also must plan out your cities well, rather than in previous games where you could get away with pretty much anything. As the Glassbox engine has actual traffic, you have to plan out your road network well, there are also additional things you have to think about, with the smaller city sizes, you probably can't handle Residential, Commercial, Industrial, and a specialization (Gambling, Mining, etc.) all in 1 city. So you have to decide what you want to focus on, and then get a friend, or claim another city, to build with the other city in mind. If you focus on Industrial, you'll probably want a Residential city as well, so you can get commuters to fill up the jobs in your city. There's a lot more to think about in this one.
The most talked about feature of the new SimCity though, is probably the multiplayer. I have to admit, I haven't tried the multiplayer mode out yet, as I'm still learning how to run a decent city, but I have run 2 cities on my own. In multi-city play, up to 16 cities share a region, what each city does will affect the region, the most obvious of these would be pollution. An industry city will output much pollution, and will lower the air quality for cities in the region. Also trade deals can be negotiated, such as trading water/power, as well as exporting/importing resources such as coal, oil, plastic etc. (Coal and Oil are required to power their respective power plants). Cities can also volunteer emergency vehicles to serve specific cities, and they will respond when the cities own emergency services can't handle the problem on their own. These emergency vehicles are separate from the ones serving in your own city, so you can volunteer however many are available, the more emergency stations/garages you have, the more you can volunteer. This does come in handy if someone is just starting up in a region, and there's another player with a decent sized city, they can handle the small cities emergencies for them, while they spend their money on getting started. This feature seems to work fine, and it's a great addition to SimCity.
The graphics on the game are decent, and they don't require an overly powerful graphics card to run, my HD7850 runs it on max settings at 60FPS, for a 2013 game, the requirements are low. Not a great deal to say about the graphics, they aren't too impressive, but they're not poor either.
The sounds are good in the game, you can hear emergency vehicles drive around your city, each individual traffic makes a noise as it passes the camera, and busy areas have the generic city sounds. Also certain buildings will make noises when you are near them.
Not all is well though, there are some faults, as I'm sure you're very well aware.
The always-online DRM can be annoying, especially if you have pretty severe internet connection problems, or you don't actually have internet where you play.... then you can't play it at all.... I haven't really got too much to complain about this personally, there was a 4 hour period one night where I couldn't play due to my server having issues, but that's the only time I've not been able to play, or affected by the Always-Online DRM. I'm sure it was more frustrating for the first week or so, but by the time I got the game, the problems were mostly fixed, although some features were missing, most importantly Cheetah speed, though I probably wouldn't use that much, it's hard enough to keep up with what's going on with Llama speed.
Another downside to the new SimCity, is that EA didn't seem to think anyone would want to play SimCity on their own, which, obviously, some of us do. The game is clearly geared toward multiplayer, even the Always-Online deal is related to that. If you try and manage more than 2 cities, they'll be growing at an exceptionally slow rate, as city simulations are paused when the owner is not present in the city, so you'd have to switch between all your cities every now and then to keep them growing... Luckily they will still send aid to you, and affect gameplay, even if the owner is not present. For a game that's always been 100% single-player, I think it was a mistake to suddenly make it 75% Multiplayer and 25% Singleplayer, for better or worse, you can't play the new SimCity like you played the old ones. If you have a couple of friends who like SimCity, and you play together, it'll greatly improve your experience.
I haven't seen any disasters yet, although from what I've read, they're extremely rare (at least at the moment) and only happen every few hours. Fires are however, commonplace now, and are not viewed as disasters, and in a fairly large city, there will probably always be a fire going on at some point.
Overall, I would say, that despite all the problems with this game, it's still my favourite in the series.
If you like the series, you should definitely buy it, most bugs are fixed, or will be fixed shortly.