Bitcatcha reports SiteGround's page loading time to be 148ms, and Google recommends anything under 200ms. Bitcatcha also brings up the important point that the regions closest to your data center will have the fastest response times. So make sure that you place your data center close to your target audience.
HostingFacts reported the speed as 714ms, which is pretty fast for their records. The data also didn't have a lot of variabilities so the website speed will not vary too much between uses.
This user rated SiteGround's load times: 5.0