I have a x750e (x550e with 8 ports i believe) and a x700.
Installed 1.2.3-RC-1 onto the internal 128Mb CF card and the unit booted perfectly and is currently running. But its very tight on card memory.
I bought a kingston 8GB CF and installed nano (1.2.3 release). The unit wouldn't boot. Installed the full system on the card and the same no boot
put the same card in the x700 (slighly older with a slower 1.2 mobile celeron, 6 ports and different gubbins)
the card was read, but the full install fais with a dma check on the CF card.
put 1.2.3 embedded (nano) and the system booted ok.
Therefore i must conclude that the reader/interface in the 750 does not like the bigger, faster newer cards.
The 750 appears to be the better specked system with 8 Gigether ports a 1.3 intel and ddr2 memory (2 slots), But on the downside has wierd hdd interfaces I've not seen before. (micro connectors and no standard 40 pin hdd headers.)
the 700 is smaller and quieter 1 pc133 slot for memory, 6 realtek ether ports and the slower proc and mentioned earlier.
this also has a miniPCI with an encryption card in, which i believe is not supported on freeBSD, but if i can lay my hands on a wifi card the slot may get used.
I'm going to swap to the 700 with the nano on 8GB CF card for my main router and fiddle with the 750 when i've got some more time.
looking to fit a hdd somehow as there is room for a laptop drive and do a full install or try to find a smaller compatible CF card.
only issues were some errors on phpsysinfo, which worked fine on the 700, but obviously not with nano.
The display works fine on both and the 700 has a prettier white display so may stick with that.