First, when you're creating single-serve sweets, there may be some waste. For example, if you use real eggs instead of egg beaters, a small portion of the egg is usually all that's needed. You may be able to refrigerate--or even freeze some leftovers to get around this. Bananas, for example, freeze really well, and you can keep a beaten egg in the fridge for a few days. Unfortunately, this just goes with the territory of micro-sizing recipes.
Second, be careful (but not crazy obsessed!) with your measurements; because we're mixing on such a small scale, little changes to the suggested measurements of the ingredients and instructions can affect the outcome of the finished treat in a not-so-great way. That being said, if you make a change that seems to get a better end product, let me know--I'm always open to suggestions!
Third, be careful with extracts and other powerful flavors. Again, we're working with small quantities, even a drop of stronger extracts can become overpowering, especially in frostings. Dipping a toothpick in the flavor you want to use and then swirling it in your mix is often the best way to go to get the right balance of flavor.
Fourth, these recipes were tested in my kitchen--and only my kitchen. I use a newer gas oven, but the accuracy of oven temps varies widely. So, if it looks done, but my instructions are telling you to bake it for another 5 minutes, take it out and give it a toothpick stick!
Now go have fun and try out a recipe!