I only free handle tarantulas if the purpose is to take a close look at the spider or show that tarantulas are not really like they are portrayed in movies.
Tarantulas are venomous animals but there are no documented case of a human fatality after a tarantula bite. If you get bitten it sure will be some pain from the venom itself and from the fangs. The symptoms caused by the venom can be quite unpleasant such as swelling, severe pain, problem with breathing and cramps. The severity of these sympthoms vary depending on the species.
Some species are calm and can be picked up while others may bite if they are disturbed. If you are not 100% sure when you picking up a spider it may fall to the ground – and if it do it will most certain injure the spider. The abdomen rupture easily in a fall and you end up with a dead spider.
Instead of free handle the spider you can use a empty plastic box and gently push the spider into the box. Put the lid on and the spider is safe. After you have transfered it to a new cage you put the lid off and gently push the spider back in the cage. This can be done with fast and aggressive spiders aswell, just place the box over the spider and slide the lid under. I use the same way to handle spiderlings.