Used this product a few times in the last 6 years to re-paint 4 rooms of the house. First of all, don't expect to appreciate it in the first 5 minutes. As with any tool, it takes some time and practice to get used to it and fully benefit from it. But once you get the tricks (re-filling, triggering at fixed intervals the handle, rolling), then it becomes evident that you did a good purchase. My record is re-painting the 4 walls of a 12x10 room in about 15 minutes (one coat)! You basically save the time of re-wetting your roll in the pan hundreds of time. You roll, roll, just roll. Re-filling is fast and have about enough in the container (bar) for a 8-10 feet wall if you have good quality paint with high coverage (I was using Sico Cachemire).
Then comes the washing... That's the only negative point I found of this tool. It's a bit long to do. To thoroughly rinse and wash it, you must basically dismantle quite a few parts. Better do this task in a bath with 2-3" of water (with a bit of soap). Just too long to do if you switch back-and-forth between primer and colors, like if you do two rooms at the same time or 2 colors in a same room. It's getting already more convenient if you use the newer paint+primer 2-in-1 products. But I resolved the problem another way: I appreciate so much not constantly going to the pan and saving time, that I purchased a second PaintMate to avoid having to clean until the job is completely finished (two coats without cleaning).
For the ones who complain about leaking valve, never happened to me, but I do what I always did for any silicone/rubber gasket: I lubricate them with silicone grease to maintain their flexibility and ensure they never dry/rigidify. Special rolls are a bit more expensive, but they are good quality and last several rooms if well cleaned and stored.