I keep getting them from very smart, very security conscious people. However, to make my point:
I love what they offer but…
Some do offer a preview, but users aren’t used to seeing that and unfortunately won’t care (ie: they are so used to getting them without preview, they won’t expect it or demand it).
As a coworker pointed out, there are potentially plugins for Firefox etc. (I couldn’t find one that worked) or you can use a site like this:
It’s already come in handy for me a few times.