Love it. I've always preferred high resolutions so UXGA on an 15" LCD is actually much more readable than on a 6-yo 19" CRT. It is DEFEINTELY not for everyone though, you really should see it on another laptop before you make a decision.
There are 4 main drawbacks to a higher-res screen:
1) a bit heavier. Probably not that noticeable compared to SXGA+, but you notice all the "ideal" weight calculations on manufacturers' sites are using XGA resolution.
2) Need to run higher backlight brightness in the sun - smaller fonts are harder to read when the contrast washes out. Also, for the same reason the mouse cursor can be a bit difficult to find
3) Slower graphics updates. What would run smoothly at 1024x768 may start to stutter a bit at 1600x1200 - since the app has to "paint" on more of the screen to cover the same proportion of it. This is especially true if you use applets with large fonts or high levels of transparency (like a dock).
4) "Slower" trackpad movements, especially if you like the "enhanced precision" acceleration mode. With a 1600x1200 screen it has to travel a longer distance. And using the highest speed setting without enhanced precision doesn't give you pixel-level control over the cursor. Third-party mouse/mouse drivers.
Other than these extremely minor gripes (I doubt (m)any would even notice them), I absolutely love having the extra real estate available.