the RevA and Lowers are over a year old and alot of cards where stopped with the 4.5.0-10 and new cards had to be released but R4i-Gold RevCs could pass the latest check already, but a few cards found a way to get by using Demo headers which skipped the check but will most likely be stopped for good after the next update
r4ids.cn have released as many updates as they possible can for there older cards and all up to rev C are compatible with 4.4.0-10 and DSi 1.4.5
but Rev is the only one that can do 4.5.0-10 for now but they are working on a way to try and get the other up to 4.5.0-10 as well
It would be interesting to know if there are also different revisions of the Gold Plus cart.
When there are no, that would mean that even the oldest Plus carts can support the newest 3ds OS.
And in my eyes, this would be an advantage of the Plus cart, because you know, that when the cart gets blocked, they will try to fix that in software and not just release a new cart.
Correct me if I am wrong.
P.S.:
well any that where bugged, good retailers have replaced for the people having trouble with the latest cards for the cost of postage
The postage to china is very high, when you see it in relation to the price of the cart. And you would have to wait a loong time before you get your new cart, by which time the new cart could be already outdated again.
Also, maybe this thread could be merged with this one: http://gbatemp.net/threads/what-are-the-differences-between-r4i-gold-and-r4i-gold-plus.342989/