Actually I was in the same situation with a different laptop.
Tested the Seagate: maxed out at 117MB/sec read and write. Appears to be some kind of limit, as that was quickly reached as the test sizes increased and then stayed there (+/- 3MB/sec) throughout the test.
Tested the Crucial m4 256GB mSATA: hit 233MB/sec write and 443MB/sec read.
If you can afford it, a 256GB mSATA SSD for boot and a 512GB SSD (2.5") for data would be the cat's meow. Yes, it's $600 worth of SSD, but it's sweet.
Second to that, the mSATA for boot/OS/apps and the Seagate for data would give you most of the performance for $300 less total. You'd also end up with a total of 1TB of storage.
Just to put the Seagate in perspective: I've got three WD 600GB 3.5" desktop hard drives (Black label, 7200 RPM) in a RAID0 array, and that array posted similar read and write speeds to the Seagate all by itself. Not bad for a 2.5" drive against 3x3.5" drives, eh?