The ATI Mobility Radeon HD 4250 is part of the 4000-series which is 2 generations ahead of the 1000-series it recommends (which is why the pixel/vertex shaders versions are fine), though the
*2** ATI graphics cards are among the "budget" models and generally underpowered.
It's hard to compare notebook graphics to desktop as reviews aren't generally going to compare them head-to-head, but some generic benchmarks might offer insight:
- X1950 Pro
- Default: 4640
- SM 2.0: 1783
- SM 3.0: 1931
- HD 4250
- ?: 1016-2110 (depending on system, memory, CPU)
Unfortunately I can't find the specifics of notebookcheck.net's (their benchmark numbers above for the 4250) 3Dmark06 test. If it's the "default" then it's clearly abysmal, otherwise it's somewhat competitive.
A Tom's Hardware Guide table ranks the 4250 along with the ATI 9700, X800, X1600, etc., 7 tiers below the X1950 Pro and 6 below the NVidia 7800 GT.
Your experience will likely be "poor" on your current hardware, but what does that mean? Blizzard games in general scale extremely well to hardware, so cranking everything to low (resolution included) may afford you a "playable" game. I doubt the game developer wants it to simply be playable but something a bit more spectacular (read: not ugly), so they may be a bit conservative in their requirements.