I had the opportunity to get a couple top-end T430s and here's what I can say.
1. It's pretty much the same as the T420, except for the keyboard and native USB3 ports. I hesitate to say that the old keyboard is better because I actually like most of the layout changes - Pageup and Pagedown are now found in the arrow key cluster, for example, but the new keyboard also lacks a Context ("right click") key.
2. It's a tiny detail, but I see 10 different screws used in this thing. Everything is as solid as ever, but that's the sort of thing that suggests Lenovo isn't paying as much attention to Technician convenience as it has in the past.
3. Also, in taking the keyboard off, the top molding (for the power button and volume controls) popped off on both the units I have. Might've been carelessness on my part but I never saw that with previous T-series models. Putting that molding back on is more work than taking off the keyboard to install RAM in the first place.
4. Personal aside: I hate the textured touchpad. They do not wear well. Even if I don't use it that much, my thumb rests there and it gets schmutzy in a way that doesn't seem to be cleanable. Boo.
5. Lenovo shipped this machine with its load of Windows 8, not 8.1, even though I bought it on December 9th. There wasn't MUCH crap on it - trial versions of Norton Internet Security and Nitro 8 Pro, plus Sugarync and some Cyberlink Media Suite that don't really hurt anything. Curiously, there WASN'T a Microsoft Office Trial. The machine needed 62 Windows Updates from power-on, a number that strikes me as excessive.
6. The EFI was configured for secure boot only. I had to play around before I found all the settings to allow my USB sticks to boot. I only mention that because I had to go hunting for the settings so I could run TrueImage.
7. Both my T430s shipped with 500GB 7200rpm HGST drives.
8. I can't do an apples to apples battery life comparison because my personal T420 machine is running a slightly different OS and has a two year old battery in it, but but Windows says 6:40 on the T430 I just-now unplugged. The battery on the new guy is physically slightly smaller, but subjectively the T420 and T430 are pretty much the same weight.
I'm going to take this guys and re-sell them, but I had been thinking I might keep one. As things stand, with an Expresscard for USB3, it doesn't seem like I'd be gaining anything (100MHz and maybe slightly better battery life?) to make it worth the hassle of switching from one machine to another.