Large sequential read/write speeds (the 250 MB/s vs 100 MB/s) can be a bit misleading because it's the best-case performance for HDDs, least-impressive aspect of SSD performance (their strength is in near-instaneous seek times), and you'd rarely see either figure in practice - unless you format the drive or copy HUGE files constantly (video editing).
Hard drives are considered slow because of their random seek times - typically 10 ms, give or take. Most SSDs have random read/write latencies of about 0.1 ms - best case scenario, that's 10000% the throughput! (Even more under server workloads.)
Here's an example of the difference (c.f. the Western Digital VelociRaptor - a fast HDD):
http://www.anandtech.com/show/2944/10
I'd recommend doing some simple benchmarking/profiling to see whether your workflow would benefit (much) from an SSD. Check the CPU utilisation first - if it's close to 100% most of the time, an SSD probably won't make much difference. Next, check RAM usage and page file swapping levels - if the available RAM is low and swapping occurs a lot then you need more RAM (but an SSD would also noticeably help). Finally, check the disk IO (reads/writes per second) - if either the MB/sec or IO operations/sec flatlines at some arbitrary point then you can expect a HUGE improvement.
There are also hybrid laptop hard drives (e.g. a standard 500 GB HDD, with an embedded 4 GB SSD cache) that provide impressive performance for a small price premium.
