In the next 5-6 months, I will be making several professional trips to Europe, and I have been working on my travel arrangements this week. I have found it very helpful in recent years to consult online reviews of hotels. I like to stay in small to medium sized hotels that seem like they might have some elements of charm or character. What is most important to me, though, is how a hotel treats its women guests. That's where the reviews are helpful.
I pay no attention to reviews from people who complain that a hotel is 'old' or that the rooms are small or that the TV was microscopic. Information about traffic or other noise and renovation/construction can be useful, but mostly I care about being safe and being treated with respect.
One hotel I was seriously considering I am now not considering because a review from a solo woman guest noted that she was ignored by the staff at breakfast, even once she told them that she wasn't waiting for anyone, and she had trouble getting the attention of people at the front desk. I can deal with a certain amount of rudeness, especially if it is equal-opportunity rudeness, but I'd rather stay at a place where women travelers are as welcome as men travelers.
After (and sometimes during) my trips, I contribute reviews of the places I stay, including positive reviews of hotels that treated me well. I think this is important data for solo women travelers, and much more interesting than whether the pillows are too thin.
2 years ago