setTextSize Improvement

In setTextSize function of the TFT library: "Each change in size Increases the text by 10 pixels in height. That is, size 1 = 10 pixels, 20 pixels size = 2, and so on."

Why?

It 'pretty useless to use a 50px font, while it would be very useful to use a 15px font.

If the function could also accept a decimal number ... we could use the value 1.5 for a 15px font

In the way the fonts are usually defined, resizing a font is not very lightweight to do with decimal values (aliasing and stuff). I think you better look for another font (and hack the TFT library). I am not sure if http://henningkarlsen.com/electronics/library.php can provide support for your lcd, but it is a very good option (has lots of utilities, different fonts, etc)