There is more to SSDs than the read/write speed. The SSD isn't going to be 2-3 times as fast, it's going to be more like 10-15 due to latency and a lack of moving parts leading to faster access times. And that 100 MB/sec was in optimal conditions. It's usually more like 40-60. And the write speed is worse.
This'll help you understand better than I can explain:
http://ocz.com/consumer/ssd-guide/ssd-vs-hdd
Edit: Eh, that page doesn't say much. -_-
If you use an SSD for a day, going back to an HDD will feel like a dinosaur. The computer starts up way faster, apps launch and react way faster, large app suites install much quicker, etc. As an example it would usually take 30-45 minutes for me to install the Adobe Master suite. On an SSD it took me 6-7 minutes. Things that you'll notice more significantly is running a virtual machine. Almost no lag at all compared with an HDD. The difference is quite noticeable.