Any reason why you're moving from a Thinkpad to a Latitude? You seem pretty happy with your W500.
I have a Latitude E6410 and it's a pretty nice laptop with a great keyboard, sturdy magnesium alloy chassis, and excellent industrial design, though it has some unresolved bugs for me at least. (probably isolated case though - it also was involved in an accident with pancake dough about 2 weeks after I bought it that might have led to some of the issues). I would have preferred a T410 though (IMO T400s and later Thinkpads have better keyboards than this Latitude; T400 and earlier are about on par).
My little observations/advice.
-Go for resolution. 1600x900 if you're getting a 14". One of the biggest regrets on my laptop is going for 1280x800 on my laptop.
-Trackpoint on the Dell Latitudes is usually considered to be worse than Lenovo's implementation. This depends though - I personally prefer Dell's implementation (since I learned Trackpoint on my Dell) since there's a little less wiggle/dead zone on the stick since Dell uses harder plastic on their cap. However Dell's cap is more slippery since the little protrusions are less pronounced.
-Latitudes tend to have worse trackpads. Since the E6400 Dell's been using Alps trackpads and they are inferior to the Synaptics ones on the Thinkpads.
-Note that the new Latitudes have an arguably inferior keyboard layout than the Thinkpads. (6-row instead of 7-row)However, people say that the keyboards on the new ones are fantastic.
-Build wise the two should be about equal, though it might be superior on the new Latitudes. Thinkpads do feel stiffer thanks to the magnesium alloy skeleton, but Dell Latitudes have better finesse since they use magnesium alloy on the exterior (however my Latitude has a wee bit more palmrest flex than the Thinkpads I've tried)
-Thinkpads have rubberized lids. Latitudes don't. YMMV.
-If you aren't using a docking station cover the docking connector with tape or something. It's a big weak spot on the bottom and you could easily inadvertently place the laptop on a wet table or something with a spill. That's what I did with the pancake dough incident.
