Simple UI tricks, such as progress bars, redirecting user's attention using animation, or placing slower loading sections at the bottom of a page or off-screen, can often ‘fix’ a performance problem without the need to tune the underlying code.

These UI tricks are an important tool to have in your performance tuning toolbox and can be much quicker and easier than addressing the underlying issue. They can act as a holdover until you have the time to devote to the core problem. So, one should never underestimate the UI while tackling performance issues.