For work I use a Canon PowerShot A540 6 mega pixle. It has a 2.5" LCD and you can zoom in on your photos right on the camera.
Lag time, not sure if you are talking about when you click the shutter to when the actual picture is taken?
If so, then it is OK for my work but not as nice as my Canon AE1 film camera. Not sure what you need in the way of lag time for your work. The less lag time, the more expensive (and less likely a P&S) the camera will be.
Lag time for viewing photos WITHOUT the flash is almost non-existent but can be very long when using the flash.
Overall, as a P&S for my work, I like it very much. It allows complete control over the camera in that it has several shooting modes, including completely manual. But the auto setting works well.
These photos were all taken with the camera in auto setting:
(no flash on this one
)