Are tantalum capacitor and Ceramic caps Interchangeable ?

eg if i get identical ratings and voltages, if i literally unsoldered every one of these little critters i come across and swap them for ceramic .... would i run into any issues or do they have some "special" quality about using those things?

Ceramic capacitors often have a very wide tolerance and their capacitance varies with voltage. A ceramic capacitor would typically be larger than a tantalum capacitor of the same value, but would have a lower ESR. So in most applications where a tantalum capacitor is being used for decoupling, you should be able to substitute a ceramic capacitor, if it will fit in the space. OTOH if the tantalum capacitor is being used for coupling audio or for timing, then replacing it with a ceramic capacitor would not be a good idea. I replaced a bipolar tantalum capacitor by a metallized film capacitor once, but typically there may not be enough space to do this, since metallized film capacitors are normally quite a lot larger than ceramics or tantalum caps of the same value.

As with all capacitor question, the answer starts with "it depends..."

It depends on the application and what aspects of the capacitor are critical.

High CV (high capacitance) ceramics have pretty strong voltage coefficients. So a 6.3V 100uF will only give you about 40uF at 5V. Whereas Tantalums don't have voltage coefficients.

Ceramics will have very low ESR. Traditional MnO2-Tantalums have very (very) high ESR, while their newer (and safer) Tantalum-Polymer counterparts have ESRs close to ceramic.

So it depends on what is critical: the capacitance value, the ESR, or the size.