Without a quality interface and good drivers, you are all going to bump into the latency issue. Simply put, your playing will be delayed by however long it takes for the computer to process your playing, and spit out the sound.

This can range from barely perceivable (with good gear) to barely usable. You need to get reported latency down to about 2ms to have the same 'feel' as hardware. Not easily achieved without the right gear...