Ok, I found (from someone else) an even easier and nicer way to do glass text using the Eye Candy plug ins. There is a free limited version (doesn't have all of the filters, but it does have glass) of that plug in here:
http://www.geocities.com/why2kspace/I downloaded it and it works great.
1) Write your text as a vector choosing the color you want it to be.
2) Convert your layer to a raster layer (Layers sub menu)
3) Using the magic wand click on one of the letters, it should select them all
4) Go to effects, plugsin, eye candy 3.1 or 4, glass. You will get a preview screen, just play around with the settings since it all depends on the font and color you are using.
5) If you want a stroke around the text, do it now (same way as in the tut for regular text). Deselect your glass text. Just type your text again using the text tool. Right click on it, choose properties. Change color of stroke and fill to white and increase stroke width to a larger number (5-8 depending on how big your font is). Add a drop shadow. Move that layer to the back of the glass text, and position it so it looks nice. Then merge the glass layer with the white stroke layer.
5) Then in the layers toolbox, change the blending option for that layer from normal to multiply. Your text should now be transparent. Sometimes I also like the look of luminance or hard light. Once again in depends on the color of the glass text and what is in the background of it.
I will do a proper tut with screenshots later.