[noggin]

My NUC (Haswell i5) booted from a Lexar 8GB USB 3.0 stick for the original OpenElec Gotham Beta 1 (and now Beta 2) installstick boot. It's also booted from the same type of stick to for an Ubuntu 13.10 Live trial. I've switched to Lexar USB 3.0 sticks for most of my stuff - even with USB 2.0 ports they are definitely faster, and appear to be pretty reliable.

Are you able to boot the USB 3.0 device from a USB 3.0 port though? That was the problem with the previous generation NUC and I believe Intel reported it was a design limitation with USB 3.0, at least for those models.

My i5-4250 NUC booted fine from an 8GB Lexar USB 3.0 stick, plugged into one of the back-panel USB3.0 ports on the NUC (there aren't any USB 2.0 ports fitted as standard on this model - though there are motherboard headers for an additional 2xUSB 2.0 ports which I haven't used)

I use this variety : http://www.amazon.co.uk/Lexar-100MB-Jump...+8GB+USB+3

(Should add I'm a fan of Lexar USB sticks. Have both my unRAID servers booting from them, a pfSense firewall running from one, and they are my USB stick of choice now. Even with USB 2.0 ports, having a fast USB 3.0 stick seems to pay dividends.)

Booted into OpenElec Installer (I'm mainly using the OpenElec Gotham Beta 1 and Beta 2 - aka 3.95.1 and 3.95.2 I think) and installed OpenElec to a 30GB Intel 525 mSATA SSD (probably not very fast but was pretty cheap) USB stick created on a mac using the create install stick script. Have not upgraded the BIOS yet, and not altered any BIOS settings away from the delivered default.

If it is relevant I've got the model with space for a 2.5" SATA drive - the NUC D54250WYKH

When I booted I was offered two options for the USB stick in the boot menu. One was prefixed with EFI, one was not. I chose the non-EFI option.