Funny you should ask! I just received my Living DNA results (a month early), and had previously been asked to provide a comparative review of it, once results came back, and I was just now examining all of its parts. I didn't need this test, had already taken an AncestryDNA test, then loaded that into FTDNA and paid for the unlock, then took the FTDNA Y67 test, and the MT Full test. Later I added the M269 Backbone pack, then the Z18 Pack. But the Living DNA presentation is enticing, and I wanted a double check on my results, plus I always want to encourage competition (even when I should probably have been saving my money!).
* Downsides: small user base so far, long wait time for results (predicted 3.5 months, actual was 2.5 months); no evidence they store your DNA sample (cheek swab) for future testing; yDNA results are almost but not quite as deep as others' tests, and no STR results for comparisons; mtDNA download does not contain all of your mutations; autosomal comparisons won't be useful until GEDmatch merges in the Genesis system; web site issues - they try to get fancy, but the page navigation and handling is buggy, and you'll see corrupt page scraps at times - this is unimportant, just a nuisance until they get it fixed (I'm using Firefox 55.03)
* Upsides: $119! still! for a test that includes all 3 genealogical DNA tests (autosomal, yDNA, mtDNA); raw downloads are immediately available for all 3 results, a 15MB text file for autosomal, and CSV files (only one column) for the yDNA and mtDNA SNP's. This is incredibly cheap for an autosomal test plus deep yDNA and mtDNA haplogroups
* yDNA: very impressive (for only $119); returned a haplogroup of R-U106, subclade R-L257, and their phylogenetic tree showed exactly the same SNP path as FTDNA down to R-U106, then a slightly different path to R-L257, a path that corresponded to YFULL. On closer examination, FTDNA has a few more SNP's than YFULL, and took my end result several SNP's farther to R-S23346 (using the Z18 Pack). But a result of R-L257 is really impressive - that is much farther than the STR test (Y67 for me), farther than the M269 Backbone pack, and well into the Z18 Pack. We will have to see if others get as deep a result. The download file has 377 SNP lines, not sure how it compares to others, or how you would use it to compare. It's my impression that it aligns more with YFull naming, so may be harder to compare with FTDNA tests.
* mtDNA: very impressive again! at only $119, it provided the same maternal haplogroup K1c2 as the much more expensive MT Full test. The result file does not list all of the mutations though (this will hamper comparisons), but was sufficient to identify K1c2. I was disappointed it did not include my one unique mtDNA mutation.
* autosomal: seems to be a standard test (680,000), is comparable to all others. I registered at GEDmatch Genesis and used the generic upload link, and in half a minute, the file was uploaded and processed (per the instructions, you wait for the word 'Finished' at the bottom). Admixtures seemed to be immediately available, and comparisons will be ready within a few minutes to a few hours, but I did not test anything there yet. The Living DNA 'Origins' like screens were essentially identical to what both Ancestry and FTDNA display, with the addition of local regions within the British Isles.
Basically, competition is a great thing! This should provide some additional downward pressure on pricing from the big 3. For anyone with limited funds that wants fairly deep paternal and maternal haplogroups plus an autosomal test for comparisons (once Genesis is ready), this is a great choice.
(My actual results are available to anyone that wants to examine them, just ask)