The elevation of Poon hill is 10475ft or 3193m. It exists in the coordinates of 28.39944̊ N Latitude and 83.69083̊ E.
Since Poonhill lies at lower altitude, there is no risk of Altitude Sickness. The highest elevation difference that you will face is while walking from Ulleri to Ghorepani. It is because at Ulleri, you will be at a height of 1500m (approx.) and Ghorepani lies at 2800m height which means you will conquer nearly 1300m on this day. For those who are wondering about the Acute Mountain Sickness and who are thinking about the trekking advice which says you can only make 500m of climb on a day, well this advice is only for those who venture on the land that is more than 5000m altitude. There is absolutely no Altitude Mountain Sickness risk in Poon hill.    
An altitude up to 3500m is considered safe for a normal person. But then you can always customize your poonhill trek itinerary and take a slow climb if you feel any technical difficulties.  
But weather in Poonhill remains quite windy. So, it would be wise to take warm clothes with you.
Although it lies at relatively less elevation, Poon hill is considered as one of the best view points in Annapurna Region. In fact, it is the second best view point in Nepal, lagging behind only by Kalapatthar view point. Kalapatthar lies in Everest region and offers great sunset view over Mount Everest. Poon hill is popular for its stunning sunrise view over Annapurna Mountain. Macchapuchhre Mountain, Dhaulagiri Mountain, Annapurna Mountain Range and other mountains and peaks can also be viewed from Poonhill.