Ranked in these QuestionsQuestion Ranking
Pro Free for open-source projects
AppVeyor is free for public GitHub repositories.
Pro The initial setup is easy
There's practically no setup involved prior to working with AppVeyor: simply sign in, add the project, and start a new build.
Pro Supports Windows build enviroment
AppVeyor has a build environment for Windows available.
Pro Allows login to the actual build VM
Pro Clear, straight-forward user interface
Well I suggest you check it out for yourself, but what I like most is that it's simple yet effective: no bells and whistles, simple black/grey/light-blue/white color scheme, it's immediately clear where you have to go for each specific task, and build settings pages are like that as well. Getting a 'standard' build running literally took me a minute the first time I used it.
Con Configuration is extremely limited
AppVeyor's configuration (which is done from the .yaml file in the root of the project) is unfortunately very limited. The configuration is either tied to a branch or, in other cases, it's global. This limits the developer to a single build process.