fair call, if i were true the prices probably would be higher as more research/testing would have been put into the drives. i dont see why they would lie though, but seeing as though they dont have a clear definition on their website then i guess we cant call it lying

(i couldnt find a page with a definition, am i missing something?)
I've not seen a definition either, and suspect it's intentional. It allows them to be vague, not only to the consumer, but keeps their IP out of the hands of their competition as well.
At best, if it actually occurs, the differential in rpm is very likely lower (i.e. it floats between say 5900 and 5400), as the spindle is the power hog in a mechanical drive, followed by the servo, and the electronics are a distant 3rd (which is why SSD uses so little power in comparison).
for new hard drives (such as the RE4), would they be somewhat similar in operating to the older (RE3s?) hard drives? are the changes THAT large that it needs a complete upgrade?
Not so much. Newer designs are usually based off the previous ones, and in the case of the WD2003FYYS, it's likely due to the lateness of it's release that it gained the RE4 designation rather than the RE3, as it seems the difference is only the platter density has changed (what the RE4 line offers btw, so it fits perfectly). It would appear as "old tech" had they given it the RE3 label.
oh yes of course, i guess they would generalise a fair bit. e.g. "the card works with this drive, so it will have to work with its v1.1" or something of that sort.
Take a look at a few. You'll see a card model #, a drive model #, and firmware revisions for
each. So detailed research is required before purchase. Where it gets hard, is if you're not getting a complete system (changing either the card or drives alone).
oh and dont i know it. the issue i have (and EVERY other Time Capsule owner) is that the capacitors in the power supply are exposed to too much heat. apple tried to make a small unit with no ext. PSU, which they did beautifully - but they didnt give it any airflow to keep it cool! so yes. blown capacitors after 18months.
Somehow, I'm not really surprised. If I had to guess, they didn't use the right capcitors though in terms of temp ratings. 105C can be had, but they likely used lower. 80C at best, and keep in mind, as the temp rises, the cacitance is reduced, further increasing the stress on the device. The rated value is usually that at ambient (25C). To know what it will do in a design, you need to heat it up, and test a few parts to create a curve. Not all manufactured component makers do this for you.

A hint as to how well it will perform too.
do you mean they arent the only ones? that would make more sense
get some sleep eheh.
Not a sleep issue, just typing too fast.
is that test conclusive? (the article i linked to earlier). the write speeds are pretty darn slow really... reads are ok.
Not really, as it's one case (and isn't working as it should). If there were more experiencing the same issue, then yes. Other tests, on similar systems that are functioning properly, would be a better indicator. Checking other sources, such as Storage Review would hopefully offer additional information.
However, given the issues are with multiple cards, I'd wait before using them. At least do as much research as possible, to see what's going on. Assuming it isn't an isolated issue (which would seem to be with the system in question, and it does happen), waiting for a solution to arrive would be the safest course of action. If the need is immediate, then look to the competition, and you have to do the research for each drive and card combination you're intersted in. Research, research, research. RAID's full of it.
