I have just completed my first 2 weeks of Invisalign and still have one more week with my first set of aligners. They are not covered under my insurance but I was adamant about getting them over traditional braces.
I have to admit, my first week of Invisalign, I hated them! The first three days were very painful so plan on eating soft food. But this only assured me that they were working. Mostly, I hated the fact that I could not speak normally with the aligners. I was seriously hating my life during the first week because my job requires me to speak to various people all day and I could not stand having a lisp and not having people understand me.
Also, I was just very uncomfortable with the aligners in my mouth. They did not cut my mouth but I just was not used to the feeling of having my teeth covered. My mouth went from producing too much saliva too being too dry. But magically, around my seventh day or so of having the aligners, my speech started to improve and I don't notice them in my mouth as much! I have noticed that if you rinse them out before replacing them in my mouth, they are not as dry and therefore are more comfortable. Another plus to this system is that not one person has noticed that I have them on (at least no one has mentioned anything)!!
All in all, my speech improved everyday and now I sound pretty normal. I also don't really notice that I have them on (unless I replace them after eating without brushing my teet). You just have to be patient with them and invest in lots of toothpaste, floss and drinking straws (I cheat a bit and use straws to drink coffee, soda and smoothies).
Also, after reading other reviews it seems that it is best to go with a reputable orthodontist. I am probably spending a bit more money because I have a great orthodontist but I think it is important to choose someone who has experience. In the end, it is up to the dentist/orthodontist to relay your dental plan to the Invisalign company.