Well, depending on the 4k video source, if you don't have support for the correct HDCP level, it's not going to play anyway.
I find browsing and working on 4k @ 30 to be very annoying, but this is subjective. It is certainly something I got used to, but still I don't like it, so 99% of the time I don't do it. The mouse feel is very noticeable different. I only switch up to 4k when I need the screen real estate, which isn't often.
It certainly works fine, but being subjective, only you can decide if it's something you want to work with on a regular basis.