Now here is a gadget tailored towards the Apple Macbook Pros, the PNY 128GB StorEdge SD Card. This is a half height SD card designed to fit Macbooks; especially for those with smallish SSD storage.
If you have a machine with 64, 128 or even 256GB SSD, you can find yourself running out of storage pretty fast. This is ideal for storage music, videos, photos.
On the 15" Macbook Pro Retina, it is pretty much flushed with a slight 'grab-able' edge. I've read it is also flushed on some Macbook Airs but it sticks out quite a bit on the 13" Macbook Pro Retina.
The retail on the 128GB is pretty hefty at $199 but I got this on sale for $60 so I jumped on it.
It mounts and looks like an external icon on your Mac Desktop.
As for speed, I ran Black Magic's Disk Speed Test and got pretty much the same results for both exFAT and HFS plus formatted file systems. Expect to get 50 MB/sec writes and roughly 87 MB/sec reads from a 15" Macbook Pro. This isn't amazingly fast but because of the convenient form-factor, it is pretty good.