Unless I am misunderstanding, HotPot is just, as you said, a mashup of data they already have - shown in a heads-up fashion. I don't see how using hotpot alone would impact the rankings, because using hotpot means you are really just interacting with the actual place page itself.
Spadilla, It's my guess that all ratings and reviews would be considered for influencing the organic ranking algorithm and the new Place Search algorithm and Google might place more trust on a rating done by a logged-in user.
I went ahead and rated a handful of Las Vegas hotels and restaurants I have visited but today a search for "las vegas hotel" has just one of them in the old-style onebox I see - the Venetian. ;) - just kidding - I don't expect one review to tip a hotel into the onebox.
After signing in, I can see my rating, so at least my data has contributed to the result in some way. The number of reviews doesn't matter, because one of them has just 239, while the others are mostly over 2000-3000+. I don't watch this SERP, so I can't say if the organic results have moved much since last week.