I'm currently working on modelling proper suspenion for the Mi-24. With springs and dampers modelled, and grip varying depending on wheel load. This makes take-offs, landing and taxiing more real. You can really notice it on the controls
When adding collective the helicopter will gradually become lighter on the wheels, and if may start skipping around if you apply some side cyclic. Pushing cyclic forward will put more weight on the front wheels, and hence make the entire helicopter tilt a little forward. As well as gaining speed if the brakes are off (or even with them on if the helicopter is light on the wheels). Braking (from forward speed) will also make the helicopter tilt forward as the weight shifts forward.
Most dangerous though is sideways speed, it may make the entire helicopter tip over, since it has a fairly high centre of gravity! So be careful to not land with too much sideway speed. Even making too sharp turns while taxiing may tip it over. So be careful!
A screenshot of uncompressed suspension:
And here it is compressed at landing:
Though screenshots doesn't really do it justice. Ideally you will have to try it. But since it's still some way off from being finished I've made a little video to demonstrate it. It's mostly me doing terrible landings
http://arneh.at.ifi.uio.no/eech/suspension-test.wmv(or if you're satisfied with a low-quality youtube video:
http://www.youtube.com/watch?v=gKb5gELlD1Y Though be warned: it's hard to see the suspenion moving in that one)