Sometimes it is good to prefer the Photoshop designs when you need to design the similar elements again and again. But it doesn't give the accurate look that an original HTML and CSS gives. It depends on the situation also, if you don't have enough time to design the images or elements, then you may also prefer Photoshop.

In order to make the photoshop designs work in web, the designer usually cuts up the design into images which is painful to implement and dreadfully slow since each image has to load or otherwise you have to implement it using CSS and then it never looks like the original design. Getting coded designs is my preferred way of receiving designs.

Yes if there are many effects.

Designing by Coding always! Normally what looks good in Photoshop doesn't look good when implemented on the web. Yeah, yeah, it's time consuming. But believe me, the result is always good this way.