Prolog implementations are very efficient at implementing back-tracking, so if you end up using a lot of back-tracking it definitely makes sense. My first prototype was started in java and it was a nightmare. Secondly, for writing the query compiler, prolog was just such an elegant language.

SWIPL has a large enough and nice enough library that it makes it feel similar to other dynamic languages (python, etc.) in terms of implementing run-of-the-mill glue code.

I'm very fond of prolog as the implementation language for the constraint checking, and especially CLP(fd). I think CLP(fd) is such a killer feature, that once people start using it in their queries, they're going to wonder how they got-on before.

I would like prolog to be a lot more feature-mature for the current age however. It needs a bigger community to help flesh the language out! So many things could be made better - better mode analysis, better type checking and simply more libraries.