I stayed at the Hotel Admiral for two nights in July 2012 as a break from hostels on my way around Germany. I could not recommend this hotel highly enough. Let's break it down --
Rooms: I stayed in a single room. The space was roomier than I'd expected, with old-style furnishings in the room and modern amenities in the fairly spacious bathroom. Everything was scrupulously clean. There was no air conditioner but the room did have a ceiling fan and the open windows meant AC was unnecessary. The TV was fine, would have preferred more pillows on the bed as both nights I had to roll up a blanket and use that as a substitute. However, I'm sure that they'd have provided with me with extra if I'd asked, so it's not an issue. My only complaint with the rooms would be that the shower curtain doesn't do much to prevent water basically flooding out onto the bathroom floor, so be careful how you angle the faucet!
The rest of the hotel: it has an old-fashioned design like the rooms, but everything is also in good condition and up to date. The wi fi cut out on me only twice and was generally very good quality in my room on the third floor. I was able to Skype no problem.
Staff: Are really lovely. The lady who checked me in was very welcoming and tolerant of my very ordinary German, although all the hotel staff I spoke to seemed basically fluent in English. Another lady, responsible for reception and breakfast during the morning, really went above and beyond. After finding out that I was in Wiesbaden to visit the small town nearby from where my family had emigrated in 1849, she went and looked up extra information on the town and its history, which she printed for me in German so I could improve my reading skills. She also loaned me needle and thread for some emergency clothing repairs, for which I was very grateful. The reception is not staffed after about 9pm but you can use your key to open the doors automatically.
Other: Wi fi, like I said, was great. Breakfast featured scrambled eggs and assortment of cold foods, great value (since it's included in the room price!) and good food, but don't go in expecting a vast array of bacon and the like. I would have liked it if the hotel were closer to the main train station but aside from that it is really ideally situated at the end of the main shopping promenade and a short walk from the Neroberg, which has a wonderful view of the whole city. The corner it's on is quiet, so no late night disturbances or anything else.
Overall: it's hard to imagine how you'd go wrong staying here. I would go back any time for sure.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.