Faster time to preg. As discussed before, there are several pros and cons. Ultimately treatments speed up the time to achieve pregnancy. Cost and multiples are some of the biggest challenges.
Many. Pros: helps you see what is happening inside your body, may help diagnose an underlying problem, quickest way to become pregnant cons: more doctor visits, cost, some treatments can increase the risk of multiple pregnancies interestingly, stress levels often decrease with treatment.
Mostly pros. Other great answers but also consider who is providing the treatments and why. You need an accurate diagnosis to get effective treatment otherwise longer and mosre cost. If you do not see a specialist then be careful to avoid trendy non-proven approaches such as supplements and herbs. Alternative medicine fine but usually as help for traditional care.