THe chances are that along with most people your drivers are too upto date. With versions 1.7.2 onwards the shaders mod is much more compatible but with any versions of minecraft before that they are very specific.
Quote from Mod Page
Graphics drivers links
If you encounter problem running this mod, try update your graphics driver.
Sometimes, latest version may not work well, you may have to install prior version that is known to work.
Below is the recommended driver for AMD noted on the shaders mod page
AMD Catalyst Drivers
Recommended versions are 13.12, 14.4.
I ran into this problem with Nvidia and had the same experience, or sometimes complete crashes.
Just to be thorough, for anyone using Nvidia, since a few updates to the mod we have a slightly different issue that we can use any Versions 32x.xx drivers, so make sure you have a driver that is 335.23 or newer Link to 64 bit version
Your performace will also depend on which shaders you are using, if you are using the unbelievable shaders these are very intensive.
Less intensive shaders would be
RudoPlays shaders - Still look really nice but much better performance
and Paulo's Lagless shaders - which are much better performance but don't look as good.
Additional Tweaks for SEUS
Once the mod is properly installed, there are a few things you can do to ensure maximum performance.
-Run the game in a smaller resolution in full-screen
-Lower your render distance
-When OptiFine is installed, try toggling "Options > Video Settings > Performance > Smooth FPS:". "ON" gives more responsive input and more steady fps, but likely lower maximum FPS.
-In Options > Shaders, enable "tweakBlockDamage", and disable "CloudShadow"
-In Options > Shaders, make sure that "OldLighting" is off