Is it worth a back-end developer's time to get into web-design and HTML/CSS
sachinag: I'm going to, as someone who cannot code, take the minority view here.  You are more valuable to your company or to your clients (if you're doing freelance work) if you know systems administration in and out.  Between crowdSPRING + PSD2HTML, you can get a decent implementation of a design relatively cheap.  There's no way to outsource "good enough" systems administration.