I noticed something during Mic's match with Stef: If you buy an Estate while inheriting Ports, you get an extra Port. Stef said this was correct and I usually trust him on rule issues like this, since he has to check these things for the new online Dominion.
I guess this is because the "when you buy this" is checked after "this" has been bought (as was similarly discussed about when-gain). When you buy it, it becomes yours, so the Estate is yours and Inheritance kicks in, so you get an extra Port (the Estate doesn't know any better, it thinks it's a Port).
Pretty cool.
Now, you can have even more fun, buy an Estate, gain a Port, reveal Trader to get a Silver instead of the Estate.