There are no "rules" for when to use pearl cotton instead of stranded cotton.  It all depends on what effect you want to achieve.  I've used it in many projects. Experiment a little.  It has quite a different look than regular floss.
This is my latest finish:
 

The leaves and and the wisteria are done with #5 pearl cotton.

Here is my entry.  It's supposed to be a sort of spooky night feeling.    Halloween projects are always fun!

Here is my most recent finish:


I've been experimenting with incorporating fabrics and watercolor pencils and crayons into my stitching.   It's a lot of fun!  The blur around the birds is from some brown threads showing through a bit.

I'm working on learning this type of stitching.  This is my 3rd completed project:

side view:

This was a really fun project. 

I've created two more:




These are a lot of fun.
 

These were fun to make.




 

I created a little freebie pattern to go with the series.  Here is preview.

(Don't use the preview for a pattern tho, the pdf (posted on my blog) is bigger and designed to fit in a 4x 6" frame!)

With the holiday ahead, I thought it was a great time to try these little humbug-style chickens:

http://blog.theflossbox.com/wp-content/uploads/2008/03/chickens2.jpg
They are cute, quick, and turn out nicely without a big fuss.
ok here is an official tutorial:

First step is two squares 3-4″, but you can make them really big or smaller.

Then cut the comb and beak or whatever other parts you want and attach them.  Note there are two variations, which affect the way the final birdie sits - check the photos at the end for the difference.
http://blog.theflossbox.com/wp-content/uploads/2008/03/chickenstep2.jpg
http://blog.theflossbox.com/wp-content/uploads/2008/03/chickenstep2a.jpg

Sew three sides together.
http://blog.theflossbox.com/wp-content/uploads/2008/03/chickenstep3.jpg
http://blog.theflossbox.com/wp-content/uploads/2008/03/chickenstep3a.jpg

Turn right-side out. You can see below, what I mean by you will get a flat square if you sew the bottom shut like this:
http://blog.theflossbox.com/wp-content/uploads/2008/03/chickenstep4.jpg

Instead you  can pull the sides out to create the humbug shape.
http://blog.theflossbox.com/wp-content/uploads/2008/03/chickenstep4a.jpg

Stuff your birdie and turn under the edges and sew up.  Don't overstuff, or they end up with a rounded bottom side, and are a little wobbly.  You can try rice too.
http://blog.theflossbox.com/wp-content/uploads/2008/03/chickenstep5.jpg

Then sew on some little black seed beads for eyes.

Here are the two results.  Note the edge you hand sewed ended up in the back on one, and the front on the other.  You could add a tail with the edge in the back, or like one of my blog-readers suggested, put on little legs on the one with the edge in the front.
http://blog.theflossbox.com/wp-content/uploads/2008/03/chickenstep6.jpg

Hope that makes it clear!

I stitched this over past weekend.

The darker colors ended up a little overly dark, but pretty accurate photo anyways.
The fill-in stitching was time-consuming, but worth the trouble.
 

I wanted to make something for Valentine's day, but I didn't want it to be too strong on the standard V-Day themes.  Here is what I came up with:

I have a bunch of old curtain rings the old owner left in the house.  I put them to use making these little "ornaments", or whatever you want to call them. 
This one I covered the ring with a piece of fabric (the design is printed on the fabric, I didn't make it myself  ):

and these are with the ring on top of the fabric:

I stitched the little pig, but otherwise I used fabrics with motifs already embroidered on.  My rings have an inner diameter of 2".  I posted the details of how I made these in my blog.