I'm transferring files over Airdrop between 2 Macs running Yosemite. Before (10.8) it was pretty fast, reaching around 30M/second. Now (Yosemite 10.10) it's around 300k/second. Is this drop in speed because of the Yosemite upgrade or is something wrong with my Mac (it's a mid-2012)?
I've noticed the same thing when I connect to a hotspot after upgrading to Yosemite, and to a lesser extent any wifi network. It seems to be an issue of new software issues and the wifi max speed.
Option-clicking on the wifi icon and selecting
Disconnect from <Network name> will disconnect you from your current wifi network, which has tripled or quadrupled speed for me when starting a new transfer. This works best when both computers are disconnected. It kind of sucks, but when you're transferring files in the hundreds of megabytes as I was, it's worth it.
Initial versions of Yosemite used some new Wifi code that resulted in some serious issues for some users. If you are suing Wifi for Airdrop (which is likely), these Yosemite-induced wifi issues could have caused the slow Airdrop speeds you experienced. Later version of Yosemite (10.10.3 and later, I believe), fixed the Wifi issue (for most users). And El Capitan maintained that fix. So, upgrading your operating system could the solution.