How much has bicycle suspension technology evolved in the last 10 years? I am thinking about both rear and front suspension. What have been the major breakthroughs that all bicycle manufacturers are now using, and what sort of improvements have there been to suspension forks from 2002 vs. 2012 as an example?
I'd say the biggest change is the shift from coil and oil shocks to air springs. Even at the cheaper end of the market most bikes designed to go uphill will be using air shock suspension. Air suspension is lighter but in the past has performed less well and been more expensive. Over the years price has fallen and performance has improved.
The other big change is the amount of adjustment that can be achieved just by turning a dial. In 2002 I had to adjust the travel of my forks by taking them apart and moving spacers about. To change the rebound I had to use a different spring and to change the damping I had to use a different weight of oil. Now I have dials to adjust all three.
Lockouts that stop the suspension moving for more efficient climbing have also become widespread and much more reliable. Initially applying too much pressure to the shock while it was locked would break it. Now it will 'blow out' and switch back into non locked mode. Cannondale are taking this a step further in some of their new bikes which offer remotely adjustable travel on the fly from the handlebar.
Ps. this a great question and would be interesting for other parts of the bike. Bikes has changed massively since the birth of the sport.
To me (and for others, I think) the greatest paradigm shift (that should become widespread in the near future, my opinion) is the inertial-controlled compression-lockout valve (Fox Terralogic, Specialized BRAIN).
These work as automatic lockouts, which make the bike stable if the rider pushes it down (like pedalling hard on a smoot uphill, or sprinting on road), but allow the suspension to work when some force is applied from below, by means of a moving mass inside the system, which closes or opens the oil valves when it moves.
Of course there have been advances in compression/rebound valve design, the "full range in half a turn" adjustment dials are great, and some extra-plush, low-stiction anodized coat on stanchions make huge difference, although they are more of quantitative improvements than real game changers.
At last, it is a pity that all these achievements of technology are focused primarily in high-end, performance oriented, racing sports market. But the fact is: every vehicle deserves some suspension system. Commuter bikes suffer badly due to the lack of dedicated suspension systems, be them forks or transport-oriented suspension-equipped frames.
Either for commuting, transporting cargo or even going around with a child seat attached, not every road is smooth (in my city, most of the streets are definitely NOT smooth), but if you want to put a good suspension fork on a commuter, you end up spending too much, having a part that needs constant maintenance, and having serious compatibility problems with fenders, racks, etc. That could be the NEXT revolution: designing suspension systems with the utilitarian bicycle culture in mind.