Issues with Slide to type

Why is slide to type so annoying??? I am very careful to type the exact word I want, then verify it before moving on the next word. Then when I'm finished I have to go back and proof read everything to figure out what the phone screwed up. When I add people names it inevitably adds a 's to the end of the name. When typing several words it will go back to the word prior to the word I just spelled and either capitalize it, or completely change the word to something else. It will not, under any circumstances, type out the word 'thanks'. It will change it to everything under the sun, except 'thanks'. Other words like 'him' become 'Jim' (I never even type the name Jim, why the world is the phone referring to Jim over him????). I type in 'that' and it will automatically change it to 'that's', 'go' is always 'do', 'them' is always 'then', and there are several other common words it WILL NOT type properly no matter what. I can even spell several words out letter by letter and it will correct to the other word. Is there an internal dictionary that can be altered to correct these errors?

[Re-Titled by Moderator]