While FTDNA is currently the only company to offer an advanced and full featured chromosome browser (the ability to analyze your results and compare matches by chromosome), MyHeritage now offers a nice integration of a simple chromosome browser right on each match page. 23andMe does not offer a browser but does show your ethnicity “painted” on your chromosomes and Ancestry does not offer this service at all.
Went the Southern California Genealogical Society’s June Jamboree, signed up and tried MyHeritageDNA. I know I am Italian and Ukraine/Polish. The Balkans and Baltic showed up but my eastern European ancestry didn’t although Irish, Scottish and Welsh did. No specific location in Italy on my Mom’s side though we still have family there. Their matches weren’t true matches and when I tried to look at the matches’ family trees I would have to spend more money between 3 upgrades. Is this how all these things work? I’m really disappointed in MyHeritage and can’t recommend it for anyone on a fixed income. This is the only one I’ve done but it has left me discouraged.
Similarly, if a person has contributed a clear and distinct minority of the DNA detected, that part of the profile may be referred to as the “Minor Contribution”. However, if DNA from one or more people is present in a mixed DNA result in roughly equal quantities, any statistic relating to the likelihood that any one particular person may have contributed to the DNA profile is necessarily reduced in value due to the inherent uncertainties regarding which DNA components may have come from either contributor.
For better ancestry and medical insights, you should encourage family members, especially parents and grandparents, to take a DNA test as well. If your family is from a specific geographical location for generations, your samples could potentially improve the service's reference panel, in turn improving results for everyone. If you’re female and take a test from 23andMe or LivingDNA, you can view paternal haplogroup information, and you get more information when one of your male family members takes a test as well.

What we would expect to find then in this example is that the two descendants of John show a very close match, and the two descendants of James also show a very close match (because we know from conventional paper based research that they are related). If all four match very closely, then that’s further evidence to add to our theory that John and James were really brothers. Not conclusive proof- but pretty solid evidence.
Each ancestry DNA service has its own sample database and reference panel made of the DNA samples collected from their users and information collected from sources like the 1000 Genomes Project. The database consists of all this information collectively. A reference panel is made of certain curated samples with known family history and roots in a specific place. The services use insights gleaned from the reference panel to give you geographical ancestry results. In theory, a larger database leads to more information available to create a good reference panel, which then leads to better results for customers.  
MyHeritage DNA is the newest kid on the block and, while their database is still growing, it is comprised of people who have tested from all of the other three testing companies (this is thanks to their free DNA upload offer). In addition to this, they have shown a clear commitment to concerns and requests by their users by promising to provide advanced tools in the future and by creating an open and optional consent policy for use of DNA data. They also offer the ability to tie in with a large database of family trees and records. We think this test has a lot of promise if they continue to respond in this positive way to users.
More controversially, some of these kits profess to tell you your biological (as opposed to actual age) by measuring the length of your telomeres (in basic terms, the caps at the end of each strand of DNA that protect chromosomes, like plastic tips at the end of shoelaces). Other tests, such as 23andMe, predict higher risks of developing serious conditions, such as multiple sclerosis, Alzheimer’s and Parkinson’s, including the test for BRCA1/BRCA2 (breast and ovarian cancer) that Angelina Jolie famously underwent, going on to have a preventative double mastectomy and surgery to remove her ovaries.
This is another feature of these genetic-testing sites – they are littered with caveats and disclaimers, forever emphasising that they’re not actual “diagnostic tests” and, if you are really concerned by your results, to seek further advice from your GP or another health professional. As has been pointed out by McCartney, when anything looks serious, ultimately it’s back to the very GP and exact NHS infrastructure that these kits profess to smoothly bypass.
At-home paternity tests have been around much longer than other direct-to-consumer DNA tests. Most of them require you to collect cheek swab samples from a prospective father and child, which you then send off to a lab to determine paternity. For non-legal use, these tests can cost as little as $15, but tests that provide verified results that are admissible in court cost a few hundred dollars. 

In addition to showing geographic ancestry percentages, some direct-to-consumer DNA tests also include insights about physical traits like hair and eye color. With 23andMe, this trait information is mostly available in the upgraded Ancestry + Health kit, but some interesting tidbits can be found in the Your DNA Family report, which is available if you opt to participate in the DNA Relatives service. 
mtDNA Tests: These type of tests look at the DNA found in our cell’s mitochondria. Mitochondria is located in the cytoplasm of the cell (surrounding and separate from the nucleus where most DNA is found) and is therefore only inherited from your mother. This means that a mtDNA test can help you understand the ancestry of your maternal line only. The nature of this test option also limits it to the understanding of deep ancestry (not so helpful for genealogists)–although the more detailed the test, the more accurate and specific your results become. The most commonly used tests for this purpose can be found through Family Tree DNA (FTDNA) and they have a huge amount of helpful information on better understanding the science and genealogical significance of this method of genetic testing.