The jet fins have been popularised by the DIR revolution, there is a lucid an thoughtful argument for there use here;
DIR Diver - Fins
I personally think they have there place (the 60's), they are heavy, expensive, difficult to get a pair that fits and because the bottom section of the foot pocket starts at the bridge of your foot they tend to cramp you if you use anything but a frog kick. If you still have your Quattros and like them whey bother changing them? You can purchase spring straps for them for around £15-20. If you are set on a pair of this style then look no further than eBay and get an inexpensive clone of the Scubapro ones to try or ask on here there are plenty of people who are kind enough to meet up and let you try theirs for a dive or two.
There are however lots of people on here that will banish me to the pink mask and snorkel vault for dissing them.
HTH
Andy