You are already two builds out of date. 10061 and 10074 were released. I've done both clean installs to a virtual client under Oracle VirtualBox and a upgrade install to my Dell 15R laptop.
The one time I had a problem doing an upgrade was because there was already a C:\Windows.old. Also good to disable your anti-virus and anti-malware programs.
The reboot message still exists in 10074. MS has another month, month and a half to get Windows 10 ready for RTM. I'm not sure they are going to make it but they will probably release anyway and try to fix it after. They want Windows 10 available for the back to school crowd.
The only thing I see on Windows 10 I actually like is the improvements made to Command Prompt. I don't use Apps and still don't the flat, squared look or the continued intrusion of UAC into my use of the computer. As of now I'm planning on staying with Windows 7 on one computer and 8.1 on the other. I'll probably upgrade the laptop to 10 when it's released just so I'll have one to play with.