Yeah nearly all of the models now, IVB/Haswell, Celeron/i3/i5/i7.
From a power user's perspective: I like the i5 & up. I can tell there's a lag (very slight) on the i3 version. A regular desktop user or like a mom/grandma type of user would never notice it and my office users think they're awesome because they boot fast & open the basic applications like Office apps & Internet browsers instantly. When I have a bunch of stuff open & I'm whizzing around though, I do notice some hesitation. Nothing bad, but for me, I like things super quick with no hangups at all when I'm juggling a lot of windows & tabs. And it's more to do with the processor than anything because my standard build is a 400/500 MB/s mSATA SSD & 16GB RAM, so it's not like it's slow at loading apps or choking on a RAM limit.
The Celeron versions have more of a performance hit. They run one or maybe two applications well, but if I'm running Windows 7 and installing OS updates while doing other stuff, you can really feel the CPU start to slog down. It's pretty zippy beyond that though, so for a kiosk or basic Word/Internet machine, it'd be fine. All depends on the intended usage.
I've been backlogged lately, but I do have a pile of new Haswell NUC's (Intel & Gigabyte) waiting to be setup - I'm curious to see how the Haswell i5 vs. i7 fares. I'm betting the i5 will be the model to get for cost vs. performance. I can tell a big difference between the Celeron, i3, etc. as a power user. I am interested to see how the Iris Pro fares, since you're kind of stuck with integrated graphics no matter which model you get.