I should mention that there are caveats and downfalls for all circuit simulators out there. In a lot of cases, you have to be careful to model in parasitic inductance, capacitance, and resistance, especially when using the basic "ideal" elements. Voltage sources, capacitors and inductors always have some series resistance. Every circuit node has a certain shunt resistance and capacitance to ground. There's no such thing as a ground node (pure 0 potential) in the real world! All your circuit traces or hookup wires have resistance, inductance, and capacitance. Board layout can be critical in many circuits. Components have temperature dependencies that are often overlooked in simulation.
The big trick is to know when and where those those terms will make a difference in your simulation and coming up with good estimates for their magnitudes and there's no good way to get there except through study and experience.
