You can access Atlantic City from most mobile devices... and from your desktop or laptop ... by clicking Go to Atlantic City or pasting http://m.mafiawars.com/mobileweb into your browser. You'll see this
The best thing about Atlantic City is the ability to collect from properties in all 6 cities at once, rather than going city by city within Mafia Wars. Under 'Properties', you'll see a screen like this:
If a City has a green 'Collect' button under, you can click it to collect from the 'ready' properties in that City. The money and parts you collect will not go into your bank or vault, but it won't be left in your properties to be robbed either.
That may be the only redeeming feature of Atlantic City. The rest of the city is divided into two "mission", entitled Atlantic City Chapter 1 and Atlantic City Chapter 2.
Both Chapters have 6 jobs. each with Bronze, Silver, Gold, and Ruby levels. The jobs do not form a cohesive pattern, as in Italy's Regions. Rather, they have generic names like "Gun Down a Rival Outfit" and "Meet With Local Crime Lords." Having grown up in Philadelphia and spent literally hundreds of weekends in the real Atlantic City, I can assure you that there are far more colorful things going on there.
While you complete the jobs, the graphics look like this... and ONLY this:
You yellow meter tracks your progress towards completion. You earn Vegas dollars and the occasional low-level Vegas loot item - the highest being the Femme Fatale. The XP:Energy ratio is pretty low - topping out at 1.46 XP per Energy point - so Atlantic City is hardly the place to level up. You get 6% mastery each time you do a job, meaning you will need to do 102 jobs to complete Bronze level.
After you complete all 6 jobs at Bronze level, you will see some eye-popping graphics (for Atlantic City):
Then you do the same 6 jobs at Silver and Gold levels. You get one Skill Point for completing each job to 100% Mastery
Silver level gets you 5% mastery each time you do a job (total: 120 jobs), while Gold gets you 4% mastery (total: 150 jobs). And the jobs are not cheap, in terms of Energy required to do each one.
Ruby level is a complete drain on your Energy. You get 2% mastery each time you do part of the 6 jobs, which range from 54 to 171 Energy points per click - and you'll have to click on each job 50 times to complete it (total: 300 jobs). It takes 35,550 Energy to complete Ruby level alone. I'd like to see the Energy account that can quickly conquer that.
When you finish the 6 jobs at Ruby level, you receive the Automatic .22 (105A/99D). This is certainly a nice Weapon, but hardly worth the tens of thousands of Energy points used earning it.
Atlantic City - Chapter 2 offers an even nicer reward (the Bullet 44 OET, a Vehicle with 99A/116D stats). Even with my high-level OCD, I just can't see spending the better part of 100,000 Energy points to get through the 4 levels of 6 jobs just for one car.
The ability to collect from all your Properties at once - whether you're at a computer or not - is the real genius of Mafia Wars: Atlantic City.