My one haas a lot of play in the blade guide wheel, so when it is pushed hard, the blade cuts on an angle. Whether this is a defect with mine or typical of the model I don't know.
It has helped me out quite a few times, but just for when I needed to make a cut in a place ackward for a normal saw. I would not use it for finish work. Use a quality blade, and it cuts well and quick
Run time is OK, but it depends on material. But the battery lasts longer than I thought it would. It's important to realise that it is a battery saw, and not expect it to do loads of cuts from a 8x4 sheet of 22mm ply.
For the money, I think it is worth it for when you need a saw in a tight spot. I would use a corded for any time I need lots of cuts, or accurate cuts. If you really need a cordless for detail work or many cuts, then I would get a lithium powered one from a better brand.