Yes, I do DNA testing. My surname project, McDonald, existed well before FTDNA came into existence. (The tests were done by an academic in Belgium!). It helps some men a lot, others, not at all!
What it does do, for us, is to tell men whether they descend from our Clan "founder" in the 12th century. This is trivial to determine, a Y-37 will do it. People consider this a "big deal".
What it has also done, and this is a big warning to others, is to show that in our "main line" (which is R1a Norse Viking) an STR close match, even at 500 markers (we have about 100 of those) is not useful for reliable matching back to the year 1300. If two men are perfect matches, or 1 or two off at 500 its a good hint, but only a hint, that we should be seriously looking for a paper trail. A worse match than that means that SNP tests are absolutely needed to tell which group of Clan Donald men are in! These groups date back to about 1400-1500 AD.
BigYs come in all the time, and only 50% of the time do they confirm "family lore" or "Y-111 hints" that the man is in the group he expects.
And the Y-500 has proven useless, so far. Some of the markers in it are so slow that eventually small family groups will be helped by them.
My own line is a very rare branch, for which we got a specific marker (L175) in the very first R1a Walk the Y test, and the BigY right away found a SNP (CLD23) which so far is unique to me alone. Testing these markers is cheap and easy to get men to do. Testing positive for L175 spurred a couple of men to a burst of activity looking for paper trails.
I've written enough ... off to the local Morman Church to chase the paper trail!