Overall, Mooons was fine, but I likely wouldn't stay there again.
Pros:
*Proximity to Wien HBF train station (about a 5 minute walk).
*Recognizable building with an interesting theme.
Cons:
*Lack of attention to detail and potential hygiene issues. Staff member was noticeably sick while checking us in. Our room had eco bathroom products (which is great), but they were all low when we arrived, and the other toiletries (e.g., q-tip packs in our room were used). The bathroom lacked proper ventilation and smelled like mold. TV did not turn on.
*At checkout, we were almost charged for breakfast (17 euro per person) which we did not take.