JMAX  One of the most useful - or even essential - Mac utilities on my computer(s). I'm amazed this isn't wildly popular and that Apple hasn't bought the company.

Use it to make the Control key + almost anything into a hotkey for anything! And if you have the Apple extended keyboard (a great item itself), use its 7 extra F keys with Control, Option and Command for 28 hotkeys before you even touch the rest of they keyboard.

Examples for one-touch hotkeys on my Macs:

Mail, Firefox, Photoshop, Lightroom, iTunes, Word

And not just apps: One touch: Applications, Home Folder, Downloads, WhooHoo!

I LOVE this thing!  
(Version 3.0b9)

JMAX  I find Yep pretty buggy:

1. Unless I remember not to touch the name of the pdf while I'm tagging it, the tags won't be saved, and there's no warning to tell me this is happening - you just have to notice the doc is still in the "untagged" folder. If you're working quickly to get through a whole bunch at once, it can be pretty frustrating to look up and see some of them have to be done again.

2. Same thing's true when some tags get mysteriously combined into one, like "mac" and "camera" might be combined into a "mac camera" tag, which is worthless, and you have to go back and do it again.

3. There's the "auto-tag" function, which often doesn't work at all. That might be the good news, as when it does, a giant pile of mostly irrelevant tags gets dumped into the file. I suppose it doesn't really hurt anything, since you don't see the metadata later, but it's pretty weird and you wind up having to input the correct tags anyway.

4. Finally, the ability to select non-contiguous files by holding down the command key often doesn't work, and instead results in the prompt to the user: "are you sure you want to combine these PDF's?". Uh, no, actually, I just want to tag them the same way.

By the way, I've tried uninstalling and starting over, with the same results.  
(Version 1.7.5)