I recently tried updating a client's site to v7.0.2. The site is now missing a large amount of CSS. Reviewing the page source, the issue appears to be around the use of the "custom-style-css" ID. My client is using a premium WordPress theme that generates a custom CSS file based on the user settings in the theme menu. That custom CSS file is using the ID of "custom-style-css", too. It looks like ShareThis added it's own custom style sheet in v7, but that stylesheet is also using the id of "custom-style-css" and overriding the theme.
Please consider changing the id to something less generic - perhaps "sharethis-custom-style-css". Reading other open support threads for ShareThis about missing bold and CSS, these other users may be having the same problem with the generic "custom-style-css" as that is used in a lot of premium themes.