Invisalign is a great orthodontic solution for people who want a straight smile without wearing braces. Pros are the general comfort and discreet appearance of the aligners, and the ability to take them out when eating and cleaning your teeth. The cons include the ability to take them out when eating and cleaning your teeth (!), meaning that they only work when they're in your mouth at least 22 hours/day. Also, there are some tooth movements that are less predictable and more difficult with Invisalign, like rotations and moving teeth "up or down". The procedure usually takes longer than the same movements with braces, as the teeth aren't always "finished" at the end of the initial sequence of aligners. (They have a "refinement" phase for that)
There's another orthodontic option that is really growing called Six Month Smiles. It uses tooth colored cosmetic braces and tooth colored wires, and most treatment times are about 6 months. The procedure is designed to straighten teeth in a more simple fashion without many time consuming, complicated movements. Six Month Smiles is designed for people who want straight teeth but don't want to go through about 2 years of braces. I'm now treating more and more patients with this solution, and the patient response has been fantastic. Teeth move fairly quickly with light forces, and the 6 month average treatment time is popular. Costs less than Invisalign too. It's worth a look!