I tried Debian earlier, and its quite smooth, but I cannot for some reason dual boot that and Windows 7
This looks like an easy problem to solve. First, I would suggest re-running update-grub (because the one run by debian-installer does not always work properly), then, if the former does not help, locating Windows partition and writing Windows menuentry manually in /etc/grub.d/40_custom (there are many HOWTOs about chainloading a partition on the Net). Or maybe grub fails to run Windows EFI bootloader because it is run in BIOS mode (or otherwise); this is also easy to spot (you should have either both grub-efi package and bootmgr.efi somewhere or both grub-pc and bootmgr without extension) and easy to solve (install the appropriate GRUB package; copy grubx64.efi to /EFI/BOOT/BOOTX64.EFI on your efi partition if you installed grub-efi). Hope that helps. I can write more detailed instructions if you are interested.
Speaking of rolling-release distros, I haven't used them by myself; I tried staying on Debian "testing" for 1.5 years, but then realized that if I switched to stable, I would have the same (or even more) stability without updating 100 packages every week. Software is a bit old here (Perl v5.14.2, for example), but there are some third-party repos from which I can install new Mozilla software and new VirtualBox, and there is always perlbrew if I want a newer Perl.