30amp service will give you around 3300watts to play with. Right off the top though you'll have loads that would take away from that. Ie., converter/charger, reefer, water heater, etc...
You can get by all right, but like David said.. you can really only have 1 heavy load (microwave, A/C, hair dryer, space heaters, slide motor, etc.) at a time.
Just as an example.. you're A/C is going to need somewhere around 3000watts to kick over, then, depending on the size, 1500-2000watts while running. A microwave will drink around 1000watts when in use. It just takes a little planning.