Depending on the complex, here's a short list of things you don't have to be responsible for:

Security
This includes everything from installing electric fences, barbed wire, decent walls or palisade fencing to keeping big dogs :)

Garden Maintenance
Not always but, oftentimes, the complex you stay in will cut your grass for you. Even if they don't do anything with the flower beds, this saves you having to buy and maintain a decent lawnmower.

Municipal Hassles
Again, depending on what complex you stay at, electricity is often handled by an agent which makes things easier.  One agent I can think of here that operates in SA is "Impact Meter Services".  Call them to see what complexes they're responsible for.  The queues are much shorter and the deposits are reasonable.

So my list is really short but that was the point.  You pay more for these conveniences but, as far as security is concerned, it's well worth it.  The rest, I think, is more subjective.

Of course, there are a bunch of negatives to living in a complex.  Not least of which is the amount of control they have over what you are and aren't allowed to do.  If you can deal with those rules and limitations it can be quite a sweet deal.  Ask me, I've just moved out of a complex into a house and while the space and freedom is great, I need to fork out cash out of my own pocket to secure the house.  Garden maintenance is hard work.  Oh and the Ekurhuleni municipality is expensive (R2.2k electricity deposit!) - although pretty efficient, actually.