Last year, here in OPORTO, PORTUGAL, I paid for a very beautiful room in what was described in the site as a "annex to the main apartment and it features two bedrooms". In reality, it was just an apartment with five or more rooms, and no separation whatsoever."The video walks you through all rooms and areas of this property", they say on the page. They show you what they want you to see. AND in the house, lived the landlady and her husband, both well over 40, which was NOT mentioned in the page. I still have the e-mail they sent me confirming that she didn't live there. I am a person who would never go live with older people, I want to live with people my age. In the site the room had a key on the door, but in reality it didn't, so when I asked my landlady to put one in, she said I would have to pay for one myself and acted as if I was crazy for wanting what I paid for. Still, after all this, I still wanted to stay in the room, because school started next week and I was out of energy to look for a new place.
This was, until what came later on that first day: my landlady took me to a corner and started talking. She was clearly mentally unstable. It would take just a minute of hearing her talk, had it been possible for me to meet her before I paid, to realize this. She told me about how she was unhappy with uniplaces because they were starting to charge her more (or she was getting less money, something like that). So she was planning on leaving the site THE NEXT DAY, but still would rent the room to me. She told me to call them and say I didn't want the room, even though I still did, and she would rent it to me nevertheless, outside of the company. I said NO because I am not a person who would lie, even to a company who clearly deceived me.
Conclusion: I was left without a place to stay the weekend before school started. I, of course using another website, ended up in a room that was less beautiful but with a super cool landlady, that I knew was supercool, because I actually met her before paying her (which is just... common sense).
I want to say, Uniplaces did give me my money back. And, they acknowledged their mistakes, apologised, contacted me several times. They removed this landlady from the company. However, this does not make up for all the stress that they caused me.

If you're thinking about renting from Uniplaces, think about the kind of landlord who would prefer not to meet her prospect renters ahead. Maybe these are just people who don't want to be bothered showing the rooms. Maybe they want to make more money renting to foreigners. Or maybe, the kind of people you would NEVER rent from would just love this website, don't you think?
If you have other options (here in Portugal: sites like CustoJusto, bquarto, sapo and OLX) be wise and choose them.
Good luck