I have left the biggest until now. Ancestry.com, Ancestry.co.uk and Ancestry.com.au Is it worth the money? Well yes and no.
If you only have a go at family research a couple of afternoons a month, then you would not get value for money. If you are going on the site daily then yes, it is worthwhile having membership. If your ancestors lived in England and then moved to America, then i would suggest having world coverage. If they were just from the USA then just have the coverage for America. If they were from England and moved to Australia I would suggest world coverage. You can pay monthly and cancel at any time.
There are two things that i find disappointing with Ancestry.
When doing a search for somebody, the first couple of results look like they could be the person. Then there are long lists of searches that are way out of the information that you have submitted.
The next thing that is disappointing, is that they do not have a great deal of results for Ireland. Considering that so many Irish were our Ancestors the coverage for Ireland and Northern Island is lacking.
If you are keen at finding your ancestors and willing to spend a lot of time researching then i would recommend taking out membership on a monthly basis. If you are in Australia and want world coverage take out world membership from Ancestry.co.uk. With the Australian dollar being down against the US dollar, it works out about 10 dollars cheaper a month with the English Ancestry