I watch very carefully what is on the computer but have to say that, for me, Expat Shield did not install any "junk" at all. I use the AdBlock Plus add-on within Firefox and don't see any adverts either.
What I have done is made sure it does not auto start when Windows starts, and I have also disabled the Services associated with it - this is because when active it does slow down my internet, but when looking at Task Manager that is hardly surprising as the "Link Speed" is only 10Mbps (ie. "slow"!). In effect, I only turn it on when I want to download a programme (e.g. on BBC IPlayer) and then turn it off on completion (unless I want to stay "hidden"). From various reviews I have read, there are quite a few equally satisfactory applications out there that provide a similar service, but for me, Expat Shield works just fine in Corfu.