There are downsides. They don't set off alarms in my phone like my task app can. They also rely on physical proximity, so I cannot rely on them to boost my memory if I am in a different location than where I put the note. They are limited to my penmanship and drawing skills as I cannot copy and paste other text or images directly onto them. They can get in the way of other things (most frequently, my mouse). And they can get lost or covered themselves. For example, I just came across a sticky note that reminded me of something that it is now too late to do anything about (the necessary note was partially obscured by a flash drive).
Still, I find them more helpful than not. They are a lot easier to get to when I need to write down something quickly (usually before my thought makes its escape attempt). They generally stay where I put them no matter how many other notes that I have written since them (notes written on my phone tend to get buried down the list over time). And there is just something deeply satisfying about physically crossing something off of a "to do" list.
A sampling of the sticky notes in front of me:
A list of StarCraft II characters that have not yet been added to the cooperative mode (personal interest of mine).
The major dates of my doctoral study's milestones.
The upcoming milestones and the suggested time between them.
A list of possible blog post topics.
Possible tweaks to my interview guide.
Suggested software programs for qualitative analysis (transcription and coding).
Another list of possible blog post topics.
More suggested software programs for qualitative analysis.
My Google Voice phone number.
A note that simply says: "December 7 - Burgers." #wherearemyburgers?