Sorry that you have purchased Unified theme expecting it to look like our support site here. We don't actually run Unified, instead we use the newest theme Reboot (also for sale in the store). We've tried to provide as many screenshots as possible when viewing themes in the store to allow people to make the most informed decision on which theme is right for them.
As for speed there are many factors. The first and most important is hosting, you really do get what you pay for. If you have cheap hosting you will get slow speeds and running any forum can be demanding. It's also best to make sure you're running the CSS / JS cache if possible in Forum > Options > Global Settings which will help, and if you're using Gravatars you will want the Gravatar Cache plugin as that can help dramatically.
Uhh, seems to be my mistake by choosng the wrong theme, seems like will spent another 20 u.s. on the Reboot.
As to the speed - i got a good hosting, so thats not the reason. I really never understood what these two options are for. Now i got: Enable combining and caching of forum CSS files - enabled, Enable combining and caching of forum script (JS) files - enabled. Will see if that helps somehow, was turned off before.