What are some of the tradeoffs you’ve encountered in your personal builds?
I know most commercial machines I’ve used trade some features for sacrifices elsewhere. My first machine ended up getting recycled into a linear positioning system because it wasn’t suited for my needs as I had sacrificed for cost.
Yep, cost. I wish I’d built it with linear bearing ways and servos, rather than dovetail ways and steppers. But this cost 1/10 as much, so I could afford it, and now I have it to use, whereas if I’d waited until I could afford the nice one I’d still be waiting.
I’m sorry for your loss. It’s no fun to see ones hard work getting scrapped. But its not completely wasted as I understand it.
Any construction work is a tradeoff somehow, no matter how its done. Do you want a moving table or a moving gantry. Any construction has its advantages and its disadvantages.
I’m with @John_Bump because I did a cheap easy wooden working prototype, and now have that, helping me constructing an even better machine in pure alu/steel. Every version gets better. Ohh, we are a couple of DIY CNC pals doing this.
The tradeoff is all the work I put in to get what I could othervise pay to get immediately.
But i’m still happy 
Back in 2001 I built my first cnc machine. I was shooting for rigidity and made a stationary gantry machine. It’s been rebuilt many times. Started out HDPE and 1018 steel round bar with HDPE bearing blocks. Now it’s all aluminum and THK rails.
The number one trade off for me has been trying to get the most travel out of my Axes without loosing rigidity. I found X and Y not really an issue but Z is tough. The taller it is the more leverage it has on the frame.
I did many things to improve on it such as installing steel gussets, installing a 1" x 6" x 24" solid aluminum back plate between my gantry side plates. If I push on the top of the gantry sides with all my weight I can still get a 10thou deflection. 
Eric
I’m really glad you brought this up, I’m currently in the design phase of my first machine and I hadn’t considered this problem. You may have just saved me loads of irritation.
My trade offs have come as a result of location (SE Asia) and price (everything is expensive here!)
Because of location, I couldn’t get material in the length I needed, so ended up with a machine that is just capable of being shy of a full ply sheet
Because I have to freight in even such items as screws, switches and wire, it has cost an absolute fortune to make. And if I forgot something, it set me back weeks. So, I have spares for everything.
Before it ever made its first cut, I wanted to redesign it. The original designer made some engineering howlers.
My next machine will be made more from what is available locally.
That’s awesome that no matter how steep your incline you pushed through and made it anyways. I hope that you’re one of a few if any that have a cnc close by. Hopefully you can charge enough and be busy enough to pay back your investment. Best of Luck!
My most recent machine is tiny by this group’s standards and built to learn more about the current crop of controls and to allow me to experiment with the small space I currently have, but serves well and my plans for my next machine are based on moving into a shop space of commensurate size. The only regrets I have with my bench top are the Z axis clearance once the wasteboard/vacuum table is installed (OK for now, but I want to play with 3D) and that I designed the machine around an antiquated computer technology (XP and parallel port is a great system to learn and teaches you the basics of pulse command, but ultimately teaches you that not all hardware is compatible (usually with lots of cussing and tears when you find a modern PCI parallel board doesn’t supply enough voltage to drive your opto-isolators 
!!!
I would chose a drive system based on more bulletproof computer hardware and would build more of the system myself to both develop a better understanding/troubleshooting skill set and to avoid some of the cussing and fussing when the driver computer submitted to Murphy and that @@$#% Law of his!
I wasted 2-3 iterations on being a cheap ass. So on my current machine I used a lot more money, but it was well worth it.
Currently I’m only battling some deflection on Z. The axis is a tough one:-)
1/2" rails with brass bushings. Working on a replacement with ~5/8"/16mm supported steel rails and balls crew