An alternative way is to use the base of the figure as the target.
If you cannot draw a line to your intended target, from the centre of the firer's base to any part of the target's base, without crossing another models base, then the shot is blocked.
Using the figure itself impedes those that like to use larger or more dynamicly-posed figures, whilst giving an unfair advantage to those who use piddly little figures who are all in crouching positions.
The figure itself is just a bit of eye candy, and people should always use whatever figures take their fancy and not be penalised for being creative and/or original.
That was my tuppence, anyway...