Ah, always mess up micro = 6/9 until I think about it for half a second. Maybe a "n" suffix could have saved me there ;) For "long" numbers there's the new _ so you can say 0.000_000_1 if you so preferred for 0.1 micro (I generally see _ as more useful for high-precison numbers with more non-zero digits, e.g. 1_234_456_789). Would that be 0.1µ, 0.1u in a new system.
Veering a bit away from the 'suffixing SI prefixes for literals': Literal unary suffix operators might be slightly nicer than multiplication if they were #1 in operator precedence, then you could omit some parentheses. Right now if I want to use a unit:
$ pip install quantities
import quantities as pq
F = 1 * pq.N
d = 1 * pq.m
F * d # => array(1.0) * m*N
but with literal operators & functions could be something like
F = 1 pq.N
d = 1 pq.m