In Kiev and many other regions use of Ukrainian has been increasing and instruction in most schools is in Ukrainian. The percentage of people speaking Ukrainian "on the street" is about 30% in Kiev, 40-80% in Zhytomyr, Vinnytsya, Khmelnytskyy, Chernivtsi, Mukacheve, and Uzhhorod, 5-10% in Kharkiv, Dnipropetrovsk, and Odessa, 1-5% in Crimea, Donetsk, and Lugansk, and 80-98% in Lviv, Ivano-Frankivsk, Ternopil, Khmelnytskyy, and Lutsk (these are just approximations). Rural areas have a significantly higher concentration of Ukrainian speakers and speakers of "Surzhyk" (Ukrainian mixed with Russian), however, the most literary Ukrainian is spoken by educated individuals in the cities.
Source: http://www.tryukraine.com/info/languages.shtml Last update Feb 2016
If you're a Russian-speaker, you might have a hard time telling when someone's speaking Ukrainian. I listened to "Strelkov's" news conference after the shootdown of the luckless MH17 airliner and couldn't immediately work out why someone was repeating what "Strelkov" had just said. Then the penny dropped: he was "translating" into Russian, even though none of the words changed.