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Full user review
"Easy control peoples PC's without a worry"
Easy to use
Seems to work behind most firewalls (with users permissions)
Free for personal use
If your wanting to use it professionally the prices are expensive with a few different packages (although they are lifetime licenses). Most of these include preferred support but its only for a year.
Can obviously be used for mischievousness purposes (but the same goes to any remote program)
Can be slow (but that is usually down to a slow pc/internet connection(
If your wanting to help a friend out quickly then this program is really handy. I used to run a non profit (non commercial) online radio website and had problems with presenters setting up the broadcasting software. I tried a few different programs and even turning firewalls of wouldn't let them connect. TeamViewer however was able to work behind the firewalls with the users permission, meaning they didn't have to turn the firewall off (which is a lot safer). It can be quick depending on the state of both the users internet connection and computer and it offers some interesting features, such as accessing control alt delete, text and video chat, file transfers etc.
If your wanting to use it professionally though beware of a steep price.
Oh and for those who think this program is dodgy - A lot of programs like TeamViewer, LogMeIn etc. get classed as viruses and so on, but its a false misconception. They are programs that allow people to remotely control other people's computers so if put in the hands of a hacker/scammer they can obviously be used for dangerous purposes. However if you have a firewall/antivirus etc. set up correctly you can use it to prevent unauthorised access.