I could have noted that the Australian "staging points" I mentioned (e.g. RPL) are at the 30-35 hr mark, after which there is more navigation training. At the RPL point and beyond, diversity is certainly your friend.
abgd's mention of the Decathlon jogged my personal memory of another fantastic bit of free, pre-PPL experience. In some places owners need aircraft ferried to and from maintenance shops. I scored some good RH seat time on ferry flights and it was a great way of learning about cross-country flying and the operation of a number of aircraft types.
It's a truism that learning to fly your 152 well will stand you in excellent stead for flying other aircraft, so don't feel pressured on that score. With the possible exception of some LSA types, turning in an impeccable stick and rudder performance on the little Cessna is actually more difficult than on many sexier types you'll fly - at least the nosewheel types.