Is it possible (for pros & semi pros) to use Photoshop effectively without shortcuts? (PS newbies, as far as i know, don't use very many Shortcuts)
It's possible, yes. There are very few items, if any, which can only be addressed via shortcuts. Most things in Photoshop can be accomplished or accessed at least 2 ways.
Of course, work time can increase considerably with the fewer shortcuts you use.
Yes it is possible, but you'll be working much slower. Personally I don't use a lot of shortcuts as I've gone one better and built a configurator panel instead. It contains commonly used tools like vector/layer masks, brush and save/export presets.
Ultimately though, if everything is conveniently located, there is little time difference between a panel and a shortcut. It's when you have to go 'File>Save for Web>Save' for example that is the real time suck.
If you mean keyboard shortcuts and you're thinking of some kind of working setup where there wouldn't be a keyboard easily within reach (e.g. working on a big desk-filling tablet, or on a laptop/slate PC with a pen tablet screen and no built-in keyboard), there are tools you can set up to get on-screen buttons for some of the more common keyboard shortcuts.
Also, the fact that people have gone to the (considerable) trouble of making these tools and setting them up is itself an answer to the question: it's possible to work without shortcuts, but potentially such a frustration and loss of productivity that many people would rather hack their operating systems to get alternatives.
Here's one example I know about: an example for Windows called PaintDock (see the dark column on the left):
It's intended for a couple of specific brands of Windows 7 tablet that are large-sketchbook size and don't have a built-in keyboard. The idea is, you draw with the pen and poke the on-screen buttons with your other hand (while avoiding resting your palm on the screen). Or, you use the pen for the buttons with 'palm rejection' turned on, and have 'ctrl', 'shift' etc set up as on/off toggle switches.
It's based on free software called AutoHotkey. There's more detail and some suggested variants described in length on this long long thread. There's a variant of the same idea kicking around called ArtDock that has button selections for a wider selection of design software. Setting them up is complicated enough that I've been meaning to do it for ages and still haven't got around to it...
There are probably others. I've not seen anything like this for Mac, but I'm pretty sure it can be done. Most people doing design work on a Mac without a keyboard conveniently within reach are probably using a Wacom tablet that has its own customisable buttons, so there's less demand.