I'm not sure about countertops, but I can tell you about my kitchen backsplash installation.

Bought the tile through Lowes, and they subbed the installation out to ServicePros. ServicePros was truly awful. The first installation date never showed up, even though I called the day before and the morning of, to reconfirm that someone was coming. After wasting an entire day waiting for someone to never arrive, I called and complained and got mixed stories about why, so I know someone was lying to me.

We rescheduled, and the tiler did show up. But he was late because his car broke down. No big deal, he got right to work. He set our expectations high, because he boasted that his last job was tiling an entire bathroom for Jon Bon Jovi, or someone else vaguely famous, in NJ. But by the end of the job, we were let down by his skills. He filled in large gaps between tile and cabinets, and tiles and windowsills (3/4" or more) and we asked why he didn't put in tile. He said he couldn't cut it that small, it kept breaking.

We let him go and immediately asked ServicePros to send out a QA rep and to make things right. They did, and the QA rep said that the tile excuse was simply that, and that any tiler worth their salt could take the extra time to cut down the small pieces and do it right. The QA rep took pictures, documented everything, and confided in me that the initial tiler was a new guy and was worrisome to him, because he flew off the handle and cursed at the QA rep at another job.

Anyway, QA rep returned himself a few weeks later to correct the work of the initial tiler. He was also late, also due to car trouble. It took him all day to pull out the excess grout, repair some cracked tiles we missed, and cut things properly. But he did it. When we stood back and looked at everything... it was fine. Good enough. The wife and I grudgingly agreed it was not an A+ job, but we didn't want anymore hassle or have to use more PTO. The job was initially quoted as a 1-Day Job, and now we were 4 Days Off, all told. We didn't want our kitchen out of commission any more, either.

And ServicePros promised us a refund of some sort. That took a dozen calls, messages left, messages not returned, paperwork sent back and forth, all to get $150 back, which we had to travel to the Lowes Store to get. Another freakin hassle. They made that whole process difficult, I think, to get us to give up, but we didn't, on matter of principle. And stubbornness.

TLDR: If Lowes wants to use ServicePros for your job, think twice.