I have been to Kharkov three times. The city is quite safe, there are a lot of interesting things to do there: night clubs with incredible music, nice parks to walk there, greate restaurants, sports centers, bowling, pool...
I would recommend you to reserve an apartment in the city centre. The compony which i trust and usually work with is
http//www.apartments-kharkov.com the y have big range of nice ap and good prices. They are also very helpful, have interpreting service and transfer from the airport.
And there are so many beautiful girls in Kharkov, it is just incredible!
I enjoyed my trips there and hope this info will be helpful for someone.
Simon.