I make plunge cuts all the time when felling large trees. Sometimes this normally dangerous cut is really the safest way to go about it. It's a must when the tree has a risk of splitting, or you suspect it may be hollow or otherwise rotten inside, or if it has a heavy lean.
The key is to go in with the right part of the nose, start the plunge with the lower half of the tip and once your in a good ways I actually will turn the saw a bit and lead with the top of the tip because in this case it gives me better control of the cut. The chain needs to be good and sharp too.
DLB
