When they announced that the new iPad would have LTE and support tethering, I jumped with both feet. Boy, am I glad I did!
I had the notorious "dormancy" issue with my 4510L ever since 2.23 came out (it was worse before that), but even when it was working, I thought I was doing really well when getting 10+ mb/sec.
With my iPad, I find now that it's unusual to get less than 15 mbps, and the highest speed I've seen so far (mind you, it's only been 3 days) has been 28.8 mb/sec. And yes, that's with a speed test running on a tethered device.
It turns out that I'm probably going to use my iPad on its own more than I'm going to tether with it. That is counter to what I would have originally predicted, but even so, so far it's been more reliable, and a damn sight faster than the 4510L it's replaced.