From a technical standpoint, offloading the bulk of the simulation processing to a backend server farm is genius. It allows for much more detailed simulations without requiring a beast of a local terminal, as attested to EA's choice in being able to model down to the individual sim level but having a somewhat basic game engine that can run on a variety of hardware. But similarly, placing this processing on a distanced remote server that has to comply with consumer grade broadband connections leads to compromises: small city sizes, extended client update intervals, and, oddly, some compromises in simulation logic (see: sim/traffic travel networking issues, though those were apparent in every SimCity to some extent). And then there's the "always connected" requirement.
Though I still think SC5 will still be a worthwhile addition to the series, but not in a traditional sense. Given its compromises (plus the lack of multiple anytime save slots), it has to be played a bit differently. Each city is, by and large, disposable. Play the city to it's population cap (according to Ars the city starts imploding around 200k), then start over in another tile. I believe if the game was called "SimDowntown" or a rebrand of "SimTown" it'd be viewed in a totally different light. People that love the prior incantations of SimCity were expecting something like SC3k or SC4, but scaled up with better graphics, larger sizes, a better interface, and utilizing modern PC technologies. They got a more detailed simulation, but a game that "downsizes" in most other respects compared to prior games, which were on a "scale up" development.
I'm on the fence personally, and will reserve judgement until I've actually played the game. I do believe that modeling down to the individual sim level is a bit excessive in what is supposed to be a city/metropolitan-level simulation. Something like in SC4 or Cities XL where you can zoom in and see traffic/sims doing actions related to what the larger scale algorithms were processing is a good mix, in my personal opinion. And I also must lament the lack of a terraforming feature. I've always wanted some form of multiplayer in SC for a while, but I dunno about the current implementation. Again, it could very well be that everything meshes together into a fun game for me, or it could just be a reminder of how shallow SC5 is compared to its predecessors.