It seems like lower than 1080 resolution would be a huge disadvantage in sc2. 720 makes me feel like I can't see anything. How hard would it be to wait and save for a 1k$ laptop? I'm on the search for a new one for sc2 and I feel like that's going to be the sweetspot for value. Though if you buy this and it runs beautifully, update this thread with a review.
The big advantage you'll have with the HD 4250 over the Intel GMA isn't necessarily performance but compatibility. Some games run badly or not at all on Intel graphics (Sims comes to mind) but all games run on ATi hardware. WR2 is correct though, your budget is too low at the moment.