It is infamous for its high prices (hence the name Rip-Off Bar), and Shakky's practice of beating up customers who refuse to pay. It is also where Silvers Rayleigh can be found, as he frequents the bar whenever he is not out doing other activities such as gambling.
The Straw Hat Pirates stopped here to find Rayleigh after arriving at the Sabaody Archipelago to get their ship coated. Once found, Rayleigh informed the Straw Hats about his experience as Gol D. Roger's first mate, and agreed to coat the Thousand Sunny before the timeskip. The Straw Hat Pirates then agreed to meet back there after 3 days, which was later changed to 2 years.
After the timeskip, Shakky's Rip-off Bar was the place in Sabaody Archipelago where some of the Straw Hat Pirates went to learn about the rest of the crew, and when they would be arriving. Duval was staying at the bar after being injured protecting the Thousand Sunny, and Rayleigh was there when Zoro and Sanji arrived separately.
There are no notable differences between the pre-timeskip Rip-off Bar and the post-timeskip one.