GS Alpha,
Go for it and have fun. I went the other way round after flying big helos for an awfully long time. Where are the main differences????
One of the biggest challenges is hovering. The fact that the controls act differently in the hover can take a bit of getting used to. R22 have no hydraulics and are very sensitive. This often leads to a-lot of initial over controlling. Slow down, relax and try to anticipate and 'out think' the aircraft's movements. Lots of outside cues help enormously but look a long way out to the front and side and pick good solid references with vertical extent if possible. Many students get fixated on cues close in to the aircraft and that can also lead to over controlling.
The 'transition' from the hover to forward flight can also be a bit of a giggle. Inflow roll and translational lift will become your friends (or enemies).
Once the helo is in forward flight the controls are very similar to a fixed wing in many ways if a little more twitchy. The biggest shock, as you have already found out, are the rudder/yaw pedals! Don't forget that simply to accelerate in level flight you will need to cyclic forward, pull collective to maintain height and feed in yaw to overcome the increased torque (which foot depends on the rotation of the main rotor just to add to the fun ).
Fundamentally, if you are comfortable in the air, have the airmanship and RT in the bag, know the airspace and Air Law, as you must do in LH, then minimum hours to PPL(H) are perfectly achievable. Plus those long boring transits give you plenty of time to learn the bumble bee aerodynamics of helicopters. They only fly as they are so ugly the earth repels them as a friend of mine used to quote.
As spencer17 said, don't try to hover an airliner, I tried on my conversion, the bump was impressive
most importantly have fun, it's a whole different world and gives you a greater insight into the 'art' of flying.
pm me if you wish to know more.