Layout
The AB9 Pro shares layout traits with the AW9D Max, but it's worth discussing in isolation. Starting as we always do at the top left, we see a blue version of abit's Silent OTES cooling solution, which connects P965 MCH heatsink to voltage circuitry heatsink using a heatpipe, relying on chassis cooling to provide the airflow needed to make the Silent OTES work.
The AB9 Pro asks for 24-pin EATX and 4-pin P4 connectors at a minimum, with an optional 4-pin Molex for assisting with power to the PCI Express slots should your graphics card need it. The main connectors are on board edges, exactly where they should be. Further, the memory slots are close enough to the top PCI Express slot to make you think twice about changing your memory configuration without removing your graphics card, but depending on card it can be done.
As mentioned, the heatpiped heatsink for the P965 IC is very low profile, which is potentially a boon for those using passively cooled graphics boards with heatsinks on the back, which will protrude upwards towards the CPU. Slot layout is the expected 16e-1e-1e-1c-1c, but there's a gap between Express and Conventional where abit have chosen to place the JMicron JMB363, which provides the lone ATA and pair of SATA2 AHCI ports. That puts that triplet of ports in an odd site on the board, away from where you'll usually find them on many others.
The ATA ribbon provided is arguably far too short, and we can say much the same about the provided SATA cables too should your chassis put your disk drives in arguably non-standard positions.
SATA9 (yes, nine) -- belonging to the Sil3132 hiding under the heatpipe and positioned near the 4-pin Molex -- is going to be ignored by all but the most dedicated of SATA fans, leaving the eSATA port on the backplane as the most used connector being controlled by that Sil'.
Otherwise things are good with the sextuplet of SATA ports connected to the ICH8R and grouped around that bridge, along with the pin headers for 6 more USB2.0 ports, complementing the 4 on the backplane. FireWire headers are there too, for two powered ports (provided in the bundle), and the floppy port is tucked away under the bottom PCIc port, hinting that you should probably just connect one up as and when you need it, and possibly never at all at that. Personally, I've not used a floppy drive in a PC for a good couple of years now, so I care not where vendors put it.
There a POST code monitor, 6 fan headers (AUX1, 2 and 3, SYS1, NB1 and CPU1), and for the tweakers in the audience an ICS6311483 clockgen chip. It's a clean layout somewhat spoiled by the odd ATA placement and associated SATA ports hanging off the JMicron too, but most people are likely to just use the ICH8R SATA ports at least.
So not perfect, but certainly not horrific.