Perhaps the most important missing feature of Snippets (which I love BTW) is a preference to expand with Full Words only. In essence, this would only expand a snippet if it were preceded and ended with a space.
Here's an example use-case:
I have a number of snippets meant to help me correct common misspellings and typos. For example,
"wth" ---> "with"
however, if I try to type "growth" Alfred will turn it into "growith" which is obviously not ideal
another example, correct the common misspelling of:
"ommitted" --> "omitted"
however, typing "committed" will become "comitted" which is not correct.