It’s great if it meets your needs, and of course I try to make sure it does that for a wide range of uses.
The only thing you can currently do with custom properties in the CSV export is to set a
name property on each tile, and then those tiles will export as the value of their
name property instead of their ID.
What I’m considering is to add support for a “firstgid” custom property, which you could set on the tileset, which would then cause all tiles in that tileset to export as “firstgid + id”. Alternatively it could do this automatically, but the downside of this is that there is no real way of finding out which tileset starts counting where (as opposed to the TMX and JSON map formats, which do include this information).