Let me summarize first: I was completely happy with Manu. It was perfect.
I had a 11h layover in Rio (GIG) and found out from a colleague about Manu.
I decided -- a bit uneasily -- to do it. My worries were unfounded, Manu took
care of everything. He picked me up from the airport and delivered me back there
on time. I really appreciated that he worked with me on a Sunday, even though
he had important personal commitments on that day. He was also open about
the tour program: I sent him a fairly long list of what I wanted to see (in just 11h!)
* Corcovado and Cristo Redemtor,
* Sugarloaf (Pao de Acucar) cable car
* Ipanema and Leblon beaches
* Theatro Municipal
* Museo de Arte Contemporenea
* Muse de Arte Moderna (MAM) / Parque de Flamingo
* Catedral Metropolitana
* Mosteira/Igreja de Sao Bento
* Paco Imperial
* Igreja Nossa Senhora da Gloria do Outeiro
* Igreia Nossa Senhora da Carmo da Artigo Se
* Edificio Biarritz
* the area of Santa Teresa
The amazing thing is we managed to see a fair fraction of that, we only didn't get to the museums, the last two churches, and Paco Imperial and Edificio Biarritz. In addition
to my list we went to the old Rio near Praca XV (Arco do Teles), and several spectacular view
points. All in all, I was able to experience much more of Rio than I could have done on my own
(even if I had had a bit more time). And Manu took care of the traffic, parking, and everything else. His English is perfect, he knew a lot about the history of all the places we visited.
I can only recommend taking a tour with him, especially if you don't have much time. If you have more time, I would still recommend taking a tour with him, since you can get a good sample
of what there is to see (and then come back later to revisit your favorites).