They're compatible with most 'proper' browsers. In most cases, there's no harm in using them if they're just for additional flair. I wouldn't recommend you use white text on a white background and use the shadow to outline the text, though.
IMO, a very nice feature. I usually use a little darkened color of text as a shadow color. P.S. And please, forget about IE6. Stop supporting it once and for all.
In the current age, the only way to do text shadows cross-browser and without images, is with something like this: p#textshadow { /* for Safari 3, Opera 9.5, Firefox 3.1 and later versions CSS3 properties: horiz & vertical offsets, blur amount, shadow colour */ text-shadow: 5px 5px 5px #666666; /* For IE 8 */ -ms-filter:"progid:DXImageTransform.Microsoft.Shadow(Strength=1,Direction=135,Color='#666666')"; /* For IE 5.5,6,7 And also the element should have a width or height */ filter:progid:DXImageTransform.Microsoft.Shadow(Strength=1,Direction=135,Color='#666666'); } Code (markup):
Text shadow should only be used as to improve visually your website. Ie i use text shadow through my portfolio extensively as you can see in my signature as an visual improvement to browsers that support it. Also i use box shadow also . Css3 features are used on my portfolio for example to enhance the user experience but is not in fact needed in order for my site to function. Also text shadow is to my knowledge supported in all modern browsers.