Is the Nikon 50mm 1.4 Ai that hard to manual focus?

Is it quite hard to focus with this lens? I've heard from one or two people that it's 'extremely hard' to focus, or is it because they're beginner photographers? I'm not entirely sure what they meant by that, maybe it was to do with their eye sight or maybe the lens was a bit stiff. Or is it just like any other lens with manual focus eg nikon 18-55? Just curious.

In my experience it's very difficult to manually focus through any view finder. The problem is it's just to small for your eye to actually tell if it's in focus. In film cameras there's usually an extra focus device in the mirror and system that puts cross hairs together to tell when it's properly focused. I wish they were doing that for digital cameras but so far, to my knowledge, no one is doing it. Could be an electronic thing I guess.

Your best bet with any dslr lens is always use auto focus. The camera is usually far more accurate that your eye can be.

You have to learn how to use your camera. Usually today's photographers (newbies, I mean) let the camera do most of the work for them.

No disrespect intended. What you need to do is practice on an object - when the object is in focus, the focusing light should come on. (And the camera should beep too, if it's set to do that).

I focused manually on his (left) eye.

p.s. I have a split-image focusing screen. It looks like this during use http://www.pentaxforums.com/forums/attachments/pentax-camera-field-accessories/46417d1257354652-focusing-screen-reviews-cimg3006-jpg When the object in the middle is in focus, the two images ("split") match or line up.

Modern DSLRs make it difficult to focus manually regardless of what lens you use. The reason is focusing screens lack split prism and/or microprism reticles and don't offer the kind of contrast we had in the old 35mm manual cameras when everyone shot primes with maximum apertures of f/2.8 or faster. When zooms became the norm, and everyone went to autofocus, focusing screens got brighter and lost contrast because zoom users complained the old focusing screens were too dark and difficult to use with maximum apertures of f/3.5-5.6. There are alternative focusing screens for many cameras so you might want to check a vendor like Katz-Eye Optics to see if they have a focusing screen for your camera to make manual focusing much easier. Http://www.katzeyeoptics.com/

The focus screens used today, manual focus is annoying. If you manual focus a lot, consider getting a new focus screen with split/micro prism. This will make critical focusing much easier. You can buy and install new focus screens on Nikon DSLRs.
http://www.katzeyeoptics.com/

It's hard to focus not because its manual-focus ring is too stiff, but rather because of the extremely shallow depth-of-field.

Modern DSLR viewfinders only show a max depth-of-field of around f/2.8. If you select an f/stop below that and press the depth-of-field preview lever, you won't see any change at all. This means that your viewfinder is actually showing more depth of field than what your lens is actually set at. This obviously present problems as when your focusing through the viewfinder and think your in focus, in reality you're probably off by a bit.

The depth-of-field problem doesn't apply to lenses such as the 18-55mm because its max aperture is only f/3.5