I exactly have the same Lenovo laptop.
I upgraded the same wth a Samsung harddisk. I guess the model I used was Evo series - Samsung 840 Evo SSD Harddisk. This harddisk costed me Rs 8000/- INR (ie., 128 USD), but now the current price is much lower than this.
Since my laptop has only 2GB of RAM, the operating systems paged-memory module makes most of the running programs to be stored in harddisk itself. This made my laptop respond very slow and used to get stuck for a few seconds every now and then before I upgraded my harddisk to an SSD one.
After the SSD upgrade, I see a considerble improvement in the response time. Now the laptop doesn't free when I switch between programs. Reloading of the programs from an SSD is much faster as the file-seek time is zero in SSD since there are no mechanical heads, as many of you might be aware.
The laptop startup time has increased dramatically. It just takes just less than 10 seconds to bootup the Window 8.1 OS.
I strongly recommend people to upgrade to SSD, if you work with too many programs simultaneously or the memory in your laptop is too low and the RAM is not upgradable. The SSD really pays of if you are suffering from such bottlenecks.
If you don't have any performance issues, then upgrading to an SSD doesn't really provide you any visual difference, except that SSD is more reliable and robust when it comes to drops. If you are a frequent traveller, upgrade to an SSD.