I didn't considered the mechanical advantages, on that you are right... on another note, I already have a SDD (Samnsung 830) and it's great but it's not the definitive solution to everything, considering that they have a very short life span against a "well taken care of" HDD. I still however say that once loading times are done... there is noting much faster that the RAM where the current data is after loading.
Yes and no, please do not affirm things that are not entirely true.
Systems don't just load everything into memory at startup and then not write anything to disk until they shut down - therefore you are never operating entirely in RAM - I'm afraid that is absolutely entirely irrefutable.
Nobody claimed that an SSD was a panacea - the only claim made in this thread is that they are better performing than spinning platter drives, noticably across the whole system.