Technically the Gen10 is the fastest Microserver available, given that the fastest option you can buy the Gen8 with is the E3-1220 which passmarks ~3650, the X3421 passmarks at ~5100.
However, you can, given the Gen8 has a socket, remove the CPU and stick the E3-1265 in there which given it has 4C/8T will kill that ~5100...
No iLo is a step back, for some, but given that the iLo meant crippling the graphics capability of the machine to the iLo's Matrox G200, the 8 GPU cores of the X3421 runs rings around that, one of the guys on HSS is running some ESXi testing so we'll see how well that passes through to the VM's at somepoint over the next few days.
Theres also 2 PCI-e slots which will give a bit more upgradability.
6x SATA3 (might end up being 5, the Gen10 the guys have are the Beta and some of the documentation doesnt show the 6th port so thats still up in the air)
No drive caddy, screws into the side of the HDD and then slide into the chassis, improvement IMHO.
1xVGA 2xDP, could make this a pretty neat HTPC unit, or surveilance base..
So far the only thing thats actually a down for me is the soldered CPU, given the top unit you can buy is X3421 and only has 4 cores, theres a lot more power to be had from a Gen8 given a few £000 thrown at a CPU and some cooling.