Pros : Glassline pens are great to use for fine detail. Recommended to fire at 1500, however, I have also fired them as low as 1375 and I have been pleased. This kit has so many great colors. I purchased the kit for the colors you can not purchase individually (for me, brown & grey). However, I ended up loving some of the others that I had not considered. The price is also better for the kit and a set of tips are included.
Cons : Some of the colors can be thicker and therefore more difficult to apply. I find that frustrating. Be sure to shake the colors VERY well before using. They can be very watery also. I always test on a piece of paper before applying to my work.
Also, check your piece before firing to look for smudges & cracking if applied to thick. These can be corrected by "scratching" them off with a toothpick. It is easier than trying to wipe off small mistakes when the glassline is still wet.
Other Thoughts : I suggest firing a tester with all of the colors on it to use for future review. It is very helpful to see the "true" color after firing. I would also suggest purchasing extra tips with this kit. I love working with the tips for precision. I "plug" my tips with straight pins with the colored balls on them. Great way to keep them sealed with the tips still on. I clean my tips by letting them dry out, scraping them out with toothpick and then soaking in nail polish remover to get out the final residue. Works great!