Rabbi Berkowitz said it well. As MevinYavin quoted, "the good thing about them is once they make up their mind you can't change their mind, the bad thing about them is... the same thing.
Netfree is the Badatz of all filters. You cannot hack them, crack them, get them to open something that they even have a Chashash that there's a problem. So religiously your great with them. I myself who basically only use the internet for work related things (computer repair) and basic communication enjoy them very much and have been using them for many years. I probably could count on one hand (and I'm not a mutant) how many times there has been a not tznius picture that showed (maybe in the background of a picture of something else). And i quickly forwarded it to them to block it. There are practically no non-Jewish news sights allowed and any social media is blocked. If they fit you needs they are literally the best. The price is only 15/month ($4) as well and its on the internet, not the device.
Only when you use the internet for other things do you start running into problems. A woman would not be able to watch a shiur of a woman because its a women and all videos with women are blocked. A person who has a buisness with facebook, x (formerly known as twitter), snapchat, instagram, etc would not be able to work. Even whatsapp is blocked. They don't work with tablets or smartphones really and they only work with certain isp's. So thats their issue and there are many who it doesnt work for them.
In short; if it works for you its the best, if it doesnt work for you its the worst.
Well put.
Just a couple of haraos
Netfree is basically a crowd sourced white list. When it first started in EY, I believe it was totally free and operated on a by donation model. At that point, and even after they started charging, you had unlimited requests to have sites checked and opened so they could build a sufficiently large white list. The bachurim from Chul who used it in internet kiosks def contributed to requesting a wide number of US based sites. (I know of a particular bachur who was single handedly responsible for opening dozens of airlines, which he then used, and finished a passport...Today a choshuv yungerman in Tel Tzion) At some point they decided that the list was sufficiently large for the day to day user and today a basic subscriber gets ~15 request points per month which can be allocated to request up 15 new sites a month (if it's more urgent you can use more points to get quicker service).
On top of this they add a text based filter - scans the words on the a page and particular words will get the particular page blocked.
The image filtering started as a totally manual process where every picture was checked by a "Goy shel Internet" in India. I believe that today it may be partially automated.
They more or less operate on the shita that they will not be going to geheniom for you. If they think its not appropriate, or the site is built in a language/format that they cant filter - They will not open it. Period. I had a particular site - a game/book shop in poland which at the time offered very lucrative deals especially for stuff shipped to EY - which they wouldn't open even after I threated them that I would go use totally unfiltered internet, bec they didn't have the ability to filter it.
For better or worse they also probably offer the best Kehila system on the market - where the memuna of your kehilla can respond to your requests for stuff to be opened for beyond the restrictions of your particular kehilla. Its is used by practical all chasidishe kehillos across EY and some litvish as well.
When truly needed, they do have certain flexibility. For example Hebrew Wikipedia redirects to
www.hamichlol.org.il which is based in the Hebrew wiki with the inappropriate stuff removed. The English wiki has no reasonable alternative, so it is open. This very forum, where they blocked a particular board and not the whole site is also a good example.
They do have, when truly needed and pasked that way by rabbanim - the best solution for WhatsApp (computer) available - though they don't and will not advertise that fact.
They have solutions for working with other ISPs (for traveling or the like) - which work slower and are not as foolproof - so you wont find that advertised or offered as a first solution either.