This is great for an older laptop, especially the lower power draw. Did Transcend think ahead and implement these SSDs with 512 byte blocks? Machines that use PATA are also typically running XP, and with older bios as well. Both of these are going to have problems with the larger 4K blocks that most SSDs utilize.
This upgrade path needs to have as little problems possible for it to be useful, as well as minimal extra cost (no OS upgrade, etc.). Otherwise, like the other comments, it appears to me that it is better to upgrade the system as a whole (OS, MB, CPU, mem, and SSD).