Advantages:

Rapid production of high-titer virus

Broad host range (SINV)

High RNA replication rate

High transgene expression levels

Relative ease of manipulating genes

Stable, persistent gene expression in insects

Minimal pathology in insects

Disadvantages:

Short-term expression mode in vertebrate cells

Strong cytopathic effects on vertebrate cells

Gene size restrictions (<1Kb, ideally)

Some alphaviruses require BSL3 containment