Current Setup

 Here is my current setup

The cabinet is made of leftover 1/2" MDF and 3/4" Plywood from other projects. It's on casters so it can be pushed out of the way when needing access to other tools.
The shelf folds down and the laptop can be put in a drawer. The spindle is home made and is covered with 1/8" polycarbonite to watch for tangles. It is held on with Velcro and once removed the spindle slides out. The filament is fed through 1/4" tubing. I placed the printer on some "Bench Cookies". They effectively self level (or at least balance) and provide some isolation from vibration.

View from front showing X-axis mod using Zydac outriggers and heated build platform of my own design. I also added a couple LED's to show when the extruder and platform are being heated. I have the connection to the platform coming out the front so it can be easily removed in order to make part removal easier. It is also wired with a four conductor connector to make complete removal from the machine possible
I have some experience in woodworking and did something during assembly which I had not seen anyone suggest. I glued it together. I left anything which I assumed I would need to access later free of glue, but all the "tab and slot" connections as well as the lengths of board containing them were glued before tightening down the connectors. I also continually checked for square during assembly. I've not actually seen any other printers live to know if it makes a difference, but this one is pretty rock solid and free of racking.

Side view. I kept all the electronics on this one side and tried to keep the wiring as neat as possible.  I use connectors for the extruder motor and heater so I can easily swap them out. I currently use one of two Brutstruders at any given time. One is used for white ABS and the other for black ABS.

Rear view showing Z-axis mod.
Here I used a subset of Zydac outriggers along with some 1/4 " rod attached using L brackets and quick connect tubing fittings. I got the idea to use these as I was setting up a filament feed tube. I didn't like the idea of trying to squeeze everything inside the cabinet and since I had a crack in my acrylic plate (as well as a sag), I decided to replace it with polycarbonite and extend it out the back. Things kind of fell in place from there.
Of course I also made use of Wobble Arrestors. I plan to make use of this extended back area for another mod later.
Although not viewable I am using a Mendel Style Y-axis. I also mounted an LED light fixture close to the print head. The wood got a little hacked up on this one as I removed it to gain some Z movement, not my best work. 

Here is a circuit board I made up based on Zaggo's design. It uses one resistor and one capacitor which are mounted on the other side. The heated platform itself is below.

This is just a sandwich of two aluminum plates which I milled to accept a length of nichrome wire around the outer edge as well as a thermistor in the middle. All the wiring is contained in what is the upper plate and everything is insulated and held in with Kapton tape. The bottom plate has some relief areas milled and has 5 cylindrical magnets installed in the normal places (one is missing in this photo but added later). Then it is all drilled and screwed together before adding a 1/8" sheet of polycarbonite to the surface. You can see the polycarbonite in the second picture in this post. It is back painted with red leaving a center target for setup purposes. It has cross hatching created using a tungstan scribe and engineer's square

As you may have guessed if you read the above, I prefer polycarbonite to acrylic. I have at this point gotten rid of all acrylic within the printer. Most of it had cracked and I was doing all I could just to keep the MK4 held together long enough to print an alternative replacement. The polycarbonite on the heated platform works well. I had been using it for awhile when I noticed Nophead had attempted to use it at one point but then seemed to abandon it. I found using 70°C works well but I am going to try pushing it up a bit as a few larger parts recently had a slight warp.