My cursor started lagging after I installed 10.10.3 (and I did a clean install) on my iMac 5K. I think it lags mostly after I load a page in Safari or Chrome - the lag is small, but noticeable. It doesn't happen often, but it is annoying. It also occurs on my Magic Trackpad and on my second Magic Mouse. It's as if the pointer drags behind my motion, struggling to keep up. It lasts for about 5-10 seconds, then it is gone and works normally for a while. As I said, it usually happens after I load a page, but I can't be 100% sure this is what causes it. Also, it doesn't happen on non-BT devices, like my wired Logitech mouse or my Wacom Intuos tablet - they don't lag at all, so I'm guessing it's a BT issue. The BT keyboard works normally, but I'm not sure I would notice any "lag" there anyway. I tried un-pairing and re-pairing devices, switching BT on and off, resetting the NVRAM, changing my wifi parameters (because I thought there was some interference, don't ask) - nothing seems to work. The funny thing is, I don't think I noticed it after I installed 10.10.3 the first time (but I could be wrong there as well, maybe it was present), but only after I did a clean install (which I did for completely different reasons). I don't have any special BT or mouse software. Does this happen to anyone else?