With the exception of the case I mentioned in my PP at 17:49, we have never been told by anyone that they didn't like our house, nor led to believe that they didn't. Maybe they spent the whole stay sticking pins in effigies of us, we wouldn't have known.
It's really not about the house anyway. The two huge advantages of home exchange are (a) it's cheaper — imagine your last holiday but with zero hotel or car hire cost — and (b) with kids, at least, it's a better holiday.
When our kids were 9 and 7 we swapped with a family from Los Angeles for 3 weeks. After a couple of days we went to the Disney store, where they had an offer: 5-day tickets to Disneyland for the price of 2, but the catch was, you had to go on five consecutive days. So we did. It took us 3 days to see the whole park, then on day 4 we did something else during the day and only went to Disneyland at 6pm. So we got to see all the evening shows and fireworks, which were brilliant but most people never see them because the kids are knackered by 7pm. On day 5 we decided to revisit our favourite rides and queue if necessary. The house swap was brilliant for this because after a full day of junk food and adrenaline, we could come home and eat a bowl of plain pasta or whatever, and the kids could sleep in their own room and look at the posters and toys of their counterparts. Our daughter made friends with the girl across the street (whose family had a pool) and they had a sleepover. Meanwhile the LA family's daughter had a sleepover with our daughter's best friend.
Another time we swapped with the US, the 18yo daughter of our partners became friendly with our neighbour's 18yo daughter, who was learning English (we were living in France at the time). The next year the neighbour's daughter went to the US for a holiday with our exchange partners. We paid for her plane ticket because our neighbour was a single mum and not well off, but we had saved so much on the holiday that that was no problem. The two daughters are now pushing 40 and are still friends.