I also use a piece of plywood over some sawhorses as a work surface, though I have to be careful with it because it's destined to be some drawers for the workshop storage I recently built:
I also have an old broom maker's workbench that I use as a sharpening and fettling area. I have a grinder, waterstones, plate glass, and other related things. The workbench has a leg vise on it that I use when I can:
I recently put suede leather on the inside of the jaws of the leg vise, which makes it safe to use for final smooth planing and other detail operations on pieces. But there are no dog holes, no other workholding, and worst of all the bench is prone to wracking and wobbling.
Obviously, none of these work surfaces is close to a real workbench. I was reminded of this yet again about a week ago. I was trying to use my #4 smoothing plane to clean up some molding I'm making. The molding is for a display cabinet and has a couple of beveled edges. Those edges are coplaner, so I ripped one wide bevel on the table saw (yes, I do still use power tools, especially when I fall behind on a project). Before creating the rest of the profile, I decided to use my smoother to plane the somewhat rough edge.
Since I don't have a proper workbench, I had to use an improvised planing stop made with a thin piece of wood fixed to the end of the plywood by two C-clamps. You can see it to the left on the first picture above.
This works pretty well when smoothing the top of a flat piece of stock. And I used it to smooth and scrape the carcass and shelf pieces for the display cabinet. But this setup is prone to problems when planing at an angle. The smoothing plane has a tendency to slid up against the lip on the molding. Once that happens, too much horizontal pressure slides the piece back, rotates it away from the planing stop, or worst of all flips the piece up (sometimes resulting in it flopping onto the floor). In attempting to compensate for this, I found myself holding the knob on my smoother in an uncomfortable and odd grip in order to exert just the right amount of vertical and horizontal pressure. The good news is that I was able to smooth the beveled edges. The bad news is I ended up with two penny-sized blisters on my left hand.
So, I've found new motivation to make the workbench I've been planning for about two years now. I have hardware for a leg vise and a wagon vise (from Benchcrafted). I've built storage elsewhere in my shop so I can get rid of the old kitchen cabinets. I just need to get one other project done (after the display cabinet) and I'll be able to build a workbench.
At my current pace, that means I'll get to the workbench sometime after Christmas, which is ridiculous. Time to get into gear and get some things done.