Solid State Disks have been on the market for a while now and the prices are coming down per gigabyte which is starting to bring them into the realm of affordability. While recently searching to upgrade the disk in my Dell Inspiron 1102 net book I was offered a 128GB SSD. I didn't really think much of what it would do in the computer until I'd installed it. Once I got the thing imaged and transferred across into the net book I was pleasantly surprised by both the performance boost and also the boost in battery life. I was amazed actually. It was a much better machine than it had ever been, running Windows 7 quite well and most basic Office Apps.
I've procured a second SSD for a venerable Lenovo R500. The specs on this notebook are pretty reasonable, but with a 6 cell battery it's lifespan wasn't great. An upgrade to a 9 cell battery gave it a boost but not a huge one. Installing an SSD made a significant difference. 6 hours of battery life is easily achievable while using the net or office productivity applications. Speed hasn't really been such an issue with this particular laptop but now it's even better.
For high end gaming rigs SSDs are the norm and even in servers now we're seeing them more often. I've changed the set up in my desktop PC - boot from an SSD, with a 2TB SATA disk for data. As the price for SSDs continues to drop they are definitely worth considering for even lower end applications. My two older laptops now are going to be useful for longer and perform better than they ever have before. Consider it for your older SATA capable notebooks!