The American Rhinologic Society says:
Recent research has confirmed that sinus and nasal irrigations with salt water are helpful. Multiple devices are available for delivery however the high volume and positive pressure methods seem to work the best. Both the irrigation device and the water source have the potential for contamination and thus proper sterilization of both is critical to the safe and effective use of irrigations. Medicated irrigations are being used more commonly and may improve our ability to treat chronic sinusitis.
Sometimes surgery is needed to properly reach the actual sinuses and simple salt solutions might not be enough to really treat acute symptoms in some cases.
It should be noted that the longtime daily use might also have some small detrimental effects (most research shows benefits), despite heeding all precautions, depending on the goals of this intervention:
Neti Pot, Nasal Irrigation Pros and Cons
Cons of Nasal Irrigation
Using nasal irrigation to clear stuffed sinuses can be helpful from time to time for relieving symptoms, but a study presented at the American College of Allergy, Asthma, and Immunology in 2009 shows that it may actually be counterproductive when used regularly over the long term. The study showed that patients who used nasal saline irrigation for a year and then stopped using it for a year had a 62% lower incidence of sinusitis during the year in which they stopped.
It is worth a try if the dosage (of the salt or meds) is well measured, the water luke warm, and the water and other equipment clean. Unless your doctor advises strictly otherwise.