I’ve been running Ubuntu MATE 14.04 for about two weeks now on my laptop. My laptop is ancient, so it easily overheats and freezes with other operating systems. Not so with Ubuntu MATE. It is simply amazing in terms of speed and resource usage, even when watching HD videos. It far outdistanced Fedora 21, which is what I was been using before. It is definitely stellar for everyday tasks, like web browsing and checking email.
The only gripe I have with Ubuntu MATE is that every so often, it refuses to connect to WiFi. It may just be that my WiFi card is old (it’s a legacy Broadcom card).
Otherwise, it is simply amazing, and I would definitely encourage you to install it on a old laptop or PC tower that seems like it’s dying. Ubuntu MATE will breathe new life into it.