I have a T430s ordered and it should arrive next week. I am thinking about getting a 21" (or so) Lenovo monitor for my desk to go with it. The max resolution of the T430s is 1600x900. If I hook up an external monitor, will it be 1600x900, which will look like crap, or will the external monitor have a higher resolution? Will it mirror the laptop display, or will it replace the laptop display and my desktop will be on the external monitor? The Lenovo sales drones are not very helpful with this question.

You can mirror it if you like or extend it at the LCDs native resolution. I believe the DVI/VGA connectors can do up to 1920x1200 while the Displayport maxes out at 2500x1600.

Here's what the options look like under Win7...



Cheers.