Pros: Quiet. Powerful. Small. Excellent customer service.
Cons: Did not last for me.
The first time I had the EK res top and MCP355. It worked wonderfully for about a year. I did have a couple problems with the res top but that is for a different review. Anyway, the pump would not start. I can feel it struggling to start but it never picked up. My whole computer shut off because water was not moving through the loop.
After some troubleshooting, I successfully RMA'd it with Swiftech. No problems were given. I scrapped the EK res top thinking that was the problem and grabbed an EK DDC top and an IandH reservoir. But there was a catch. This new MCP355 had a 'Void Warranty' sticker between the stock top and pump. So I decided if it actually borked again, I would not RMA it and just choose a different pump. So I voided the warranty and replaced the top.
Worked perfectly again for a month or two, and the same problem. It struggled to turn on. I was able to get it to start sometimes by tapping it or wiggling the cables, but if I ever need to restart my computer, it will not start up again. If I'm lucky it would.
So here I am, with an MCP655 en route to my house. Hopefully I have better luck with this one. If this one dies too, then I am the reason they are breaking.