cotton knitt fabric

How is sewing with cotton knit different sewing 100% cotton?

A lot. You choose and cut your patterns differently. I use different seams, stitches and finishing techniques. If you are used to sewing with wovens then you'll need to adjust your thinking to get pleasing results in knits.

Here's a blog post by Karen LePage that you might find helpful.
http://patternsbyfiggys.com/2011/02/the-great-knit-fabric-experiment/

I think I may just stick to wovens.

I hope I didn't scare you off! There is a learning curve but it's certainly worth it to be able to make different things.

there is definitely a difference in sewing with knits vs. wovens.it's because there is stretch in knit and not in wovens. if you use a knit that has less stretch, its easier. you can use a regular machine while sewing with knits with certain tricks and esp. if your machine has a "stretch stitch"
a serger is much more friendly though and will help keep the shape of the pieces in tact without as much waviness that can happen while sewing with knits, because of the stretchiness.

you can find inexpensive knits to just play with at hancocks/joanns for around $3-4 on sale. the interlocks will be have the least amount of stretch. i find with kids clothing it's great to have the knit selections and my daughter can have extra play clothes too.

You might find this article from Threads Magazine helpful:

http://www.threadsmagazine.com/item/4584/a-primer-on-sewing-knits