I bought this to "ghetto mod" my BT homehub for increased range and it's worked really well, where I was having problems getting a reliable connection upstairs in my own house, I can now pick up my wireless from the beer garden of my local pub across the street :p
Problems with devices like this, people (IT muggles) expect a miracle cure, they don't understand that if their neighbour is trying to use the same wireless channel, it'll destroy their connection. They ask a friend and the so called "computer expert" friend suggests a new antenna, they get the new antenna and then complain when it doesn't work.
Remember that fitting a bigger antenna has two effects:
1) increased range
2) increased interference pickup range
Don't buy stuff like this until you've played with your wireless settings and tried repositioning your antenna/router, try changing wifi channels, look up "omni-directional antenna" on Google to understand how they work (and how to position them) and also make sure your wireless is the real problem! Your ISP will always try to blame you and your equipment for their own service problems. So if your internet just suddenly stops working, then something like this is not going to help!
If you do the above you'll just end up disappointed and coming back on here to complain about what is a perfectly good product.
It's good quality, it's a good price and it works well.
If you want more range, this is just the ticket ;)
Only downside? I had trouble positioning it, because the lead needs to be a little longer (by about 50cm). The connector could also do with having a 90° elbow bend to help keep things tidy.