Only you can answer that question. Is it important to you?
Alexa can get traffic information in one of two ways. If a site has Alexa's analytics script installed, it can record traffic figures fairly accurately. However, as many sites do not have the script installed, comparative rankings cannot be considered accurate, as information about other sites is only estimated.
The other way Alexa gets data is by recording information from those using its toolbar, to see which sites they visit. This information is then used to estimate statistics, but as it's not necessarily based on a truly representative sample - either of users or of sites - it's hard to say how accurate it might be.
Only you can decide whether or not you think such information is of any value to you.