... between this (p/no A000066) and this (p/no A000046)?
They are both Rev3 boards and appear exactly the same in form, fit and function but am I missing something here?
I'm about to order my first board and want to make sure I get the latest and greatest.
Thanks!
One's in stock, one isn't. If that influences your decision. 
You could ring them. I've seen them do something like that before, what looks like identical parts with different codes and different prices even.
Eriba:
I'm about to order my first board and want to make sure I get the latest and greatest.
The bulk of its usefulness is what you personally do with it, so that won't change. Plus you can always upload new firmware (bootloader) to it if really required.
Thanks for your replies, Nick.
I'm sure the A0000** code is an Arduino part number hence the query but I've spoken to Farnell and the guys there think they're the same item.
One's in stock, one isn't. If that influences your decision.
... yes, it certainly would (and, as a rule-of-thumb, non-stock items are always cheaper. =()
This will be my first foray into microcontrollers and I've been thinking hard to find a perennial problem to an elegant, and well supported, solution
The one in stock is not Rev 3 - there is no diode across the reset pullup resistor in the linked-to schematics.
Odd that the older board is more than the newer board.
There's some confusing info regarding part nos, revisions and datasheet content at various vendors.
I've now confirmed that A000046 and A000066 (the latest part number) are both Rev3 boards.
I guess there's no functional difference between the two, though.
A000066 is in stock at RS, here, so I'll order from them.
I'll need a USB cable - which connector is fitted at the UNO end?
Uno needs the big, blocky-looking B connector.
(not the mini-B found on lots of other stuff, or the micro-B found on really-small stuff)
Functional differece, no, is the same Atmel chip either way.
the big, blocky-looking B connector.
Many thanks!