I pushed back 4 or 5 of my family lines another generation due to what I found on FindMyPast, and was able to confirm a bunch of stuff that was only speculation before. Their handling of census records (at least in the UK) is far more helpful than FamilySearch's: where FamilySearch usually just gives you the individual, FindMyPast usually lists the entire household, including in-laws, lodgers, servants, and even guests who happened to stay over the night before the enumeration.
It took me most of the weekend to figure out how best to use their search page to get what I needed to find out, but once I did, it broke one of my brickwalls. My great great grandfather, George Slade, had a surprisingly common name. There were dozens of George Slades running around England at the time. For that matter, his father, William, also had a surprisingly common name. But, knowing that George's father's name was William, and finding a likely candidate for William, I did a search for all Williams in the 1851 census born five years on either side of my most likely candidate with a son George of the right age. There was only one pair who matched up correctly: my candidate. (Granted, there is at least a biological possibility that William could have been younger still, or more likely older. I would have liked to be able to run a scan ten years on either side, but that pair matched up what I already knew in so many ways that I'm relatively confident of the identification.)
I did learn to be careful about what I put in the search boxes, though. Sometimes surprising things would block search results that I knew were in their system. (Because the links I had already found on FamilySearch pointed to FindMyPast, which frustrated me no end hitting a paywall all the time.)
One thing that was kind of a thrill was that the census results gave, not just the town, but the street (and often the address). So I'd get on Google Maps and use StreetView to look at the address to see if it might be the same house that my great great whomever used to live in. Usually, I'd see a Tesco or some other recent structure, which was kind of disappointing. In a few cases, the street doesn't even exist anymore. (Or at least, not with the same name.)
But one thing I've learned is that I'm never going to tease people for giving their kids weird names again. It's kind of disheartening to do a search for an ancestor with what seems to be a reasonably unique name, only to find dozens of people with the same name and dates, even within the same county! (In one case, I was looking for an ancestor, and found a family where the father had the same first and last name, birthdate, and place of birth as my family. So did the mother. So did one of the children. It was only the other children having different names and ages that clued me in that it was a different family, even though they were living in a relatively small town [Frome, Somerset]). When I actually find a name that's easy to track, I practically stand up and cheer.
Greg