I am thinking about buying a 128GB SDD

You will not see any significant, if any change, in FPS of games. All that will happen is that the OS, applications and games will be loaded faster.

In answer to your questions:

What is the typical power consumption of these devices?
I don't know the exact numbers in watts but they are less than regular hard drives. However it's somewhat pointless being concerned about power consumption in a gaming machine as the GPU will consume significantly more watts. GPUs typically consume hundreds of watts whereas hard drives are tens of watts.

Does it use a regular SATA cable like a hard drive?
Yep

Will I notice significant increase in performance?
Load times will be reduced but no change in FPS

Some solid state drives have a "TRIM" feature, what is "TRIM" and how do I know if my SSD has it?
The wiki article explains it better than I can but basically it's a command sent by the OS to do deletes in an efficient manner for SSDs. New SSDs all support TRIM.

Does it come with software/drivers?
Depends on the model you use. If you are using a later version of windows you won't need any drivers.

How long do SSD's last before they die out? I heard that they are much less reliable than hard drives.
I can't provide evidence to prove otherwise and I can't be bothered Googling it, but I don't think this is the case. A regular hard drive seems as likely to fail as it's SSD counterpart.

Let me add to Rusting In Peace's good comments.

A SSD must read and rewrite the underlying nand chips to do an update. If the update is a delete, the "trim" command is issued to mark the space as available without doing the read/rewrite operation.

If your OS can access a sata drive, it can access a SSD without any additional drivers.
To enable the "trim" command to be passed through, the sata mode in the bios must be set to AHCI, not IDE.
Windows 7 native drivers will do this nicely.

There is a limit to the number of write cycles(not reads) that the nand chips can do.
The SSD microcode spreads this out, so no chips are over used.
SSD's will also reserve some spare chips.
With normal desktop operations, you are looking at a decade of updates. The SSD will be obsolete by that time.
Even if the limit is reached, the read capability remains, allowing you to back up the device for replacement.
Intel is now offering 5 year warranties on their ssd's.
Intel also has a reputation in the past of being one of the most trouble free SSD's:
http://www.behardware.com/articles/810-6/components-ret...
----------bottom line------not to worry.

You will find that a SSD makes everything feel much more responsive, and I recommend them.
There is no need to get the latest gen3 6gb drives, even if you have 6gb sata on your motherboard. The big benefit comes from the random access.
I suggest the Intel 320 drives are a better buy than the 510 series.

Additionally SSDRanking may help you in choosing a SSD.

The Corsair Force 3 120GB SATA 3 SDD is on sale at my local electronics store for $199.99. I think this might be the choice choice for my price range. It has SATA 3 speeds, meaning that it is significantly faster than SATA 1 and 2 SDD's. And I do believe that my motherboard (MSI Big Bang Xpower X58) supports USB 3.0 and SATA 3.

http://www.corsair.com/solid-state-drives/force-series-...

Should I reinstall my OS onto the SDD?

I believe that you have heard Corsair recalled all its 120GB Force 3 series for being defective... its been quite a messy launch for them :S But as its a good company they are recalling till the issue is fixed.

As the guy above said, you should buy Intel 320, not too expensive, best reliability and as a last point, its fast enough for standard/gaming desktop pc use.

You have to find out what kind of interface do your computer need.
As different ssd have different interface, find out their application before make a decison.

You could find 120gb good price reliable SSD at www b2cit dot com

I have an MSI Big Bang Xpower X58 motherboard if that helps any. And I do believe it supports SATA 3.