One of the limiting factors that I see is price particularly if you live outside the USA in a country with an adverse exchange rate.
One would of course think if one was really keen to search ones ancestry price would not be an object.
If this were so most people would be willing and keen to transfer there raw DNA to other databases especially GEDMATCH which is simple to do and partiarlly free .
It doesn't happen.If everyone did it ,what an explosion of useful information there would be.
I have my initial test with Ancestry.In 3 years there has hardly been any useful match updates.
My DNA transfer to FamilyTree DNA has been static too.
My DNA transfer to MY Heritage has produced constant regular updates.
Unfortunately like a previous poster I rarely get a reply to any query.
From my perspective MY Heritage has been the only useful and progressive DNA testing site,particularly for Ashkenazi Heritage.
Perhaps there is just too many companies wanting to cash in offering too little for the price.