If it helps anyone here's my 2 cents worth - For any females who are hesitant about travelling alone here, don't be. I'm a 40 year old who has travelled to many countries but not alone until I travelled to Cambodia. I felt safe during my 6 days here, I went out at night for dinner alone twice and took many day trips to temples and attractions with the same tuk tuk driver. The driver was organised through the hotel and was really helpful as we're the staff of the hotel. I found Cambodian people to be lovely, no hassles at all apart from the kids trying to sell goods at the temples but all tourists were being accosted to buy something. I would highly recommend a quad bike tour out of town as an added extra if you have the time spare to see the rural and more remote parts of Siem Reap. I did this on my own with a guide who rode a dirt bike ahead of me and was the next best thing to seeing the temples in Siem Reap.
As with anywhere, keep hold of your bags / camera, don't wear or even take expensive jewellery with you and don't flash too much cash around. I do the same at home in Australia, just use common sense and have a fabulous and memorable holiday.