I was born and raised Imperial, but I hate it. There are only 3 things that would give me (personally) significant trouble if I switched to Metric. And I could get around these with a little work:
1. I visualize height and weight of people in imperial.
2. 3C miles per hour (a pretty common highway speed limit) is 1 mile per minute. I like this.
3. I visualize temperatures in Fahrenheit (no, wait, is it thermoize? tactilize? Is there even a word for this?)
Anyway, I would gladly give up these tidbits for the switch to Metric. Even better than that, of course would be my ideal scenario:
We switch from decimal to Hexadecimal (you know, base 10). Then make an SI like system of units based on this, including time. The base unit for time would be the day, since this is the unit that is primarily hard coded into our bodies (our wake-sleep cycle). Base the calendar on the number of days since or before (negative numbers!) some nice reference point, like the day I was born, or something.
This needs to happen sooner rather than later, because it gets harder every time someone does an important calculation in some silly system like base A Metric, or (horrors!) a really retarded one like Imperial units.