I skimmed through, but having both devices, I can say this for fact:

1. The N95 is currently capable of using MicroSDHC cards up to 8GB (I have 6GB, but know several people who currently use 8GB)
2. Most microSD cards now ship with micro-to-mini and micro-to-full SD adapters, allowing you to use the microSD card in ANY size SD card slot.
3. I can use my 6GB microSDHC card in my N810 with the micro-to-mini adapter with zero issues. I'm able to fully use the card and easily swap between the two devices.
4. There is no difference, to a device, in a 6GB microSDHC and the upcoming 16GB microSDHC cards. There is only a difference in microSD and microSDHC, if that makes sense. There is no physical difference, only software compatiblities.

If you're wanting to get the most out of your devices and memory, I would personally suggest ONLY buying microSDs in the future. I will be buying a digital camera soon this year, and will ensure that it is compatible with SDHCs, so that I can use a microSDHC in a full-SD adapter to snap pics, and then upload them using either the N95 or N810.

Also, to answer one of the above questions directly, the N95 is advertised to only support 4GB because when the original N95 was released, it was not capable of using the HC cards. It was through a subsequent firmware update that SDHC cards were supported, and Nokia has chosen not to update the plethora of places in which this is written/recorded, and so leave it up to users to discover.