When using the advanced issue search interface ("JQL"), the project auto-complete widget fills in the name of the project instead of the project key. This is suboptimal:

• You have a project key, which – in typical applications – is used for identification of an object in processes that are not-so-visible to the user. Filters are just such an application where use of a key would be preferable to the use of the name, which would typically be used only for display purposes.
• Use of the project key (which cannot be changed) gives some stability to the filter. Instead, use of the project name means any change in project name will cause user filters to break en masse. I had just such a scenario earlier this week where I changed the name on 50 projects. I got a lot of flack from my users because their filters broke and they had no idea why. My users are software developers, so most of the flack was directed toward Atlassian for the poor engineering decision.