Both the stands I've built were around 4' tall (44" I believe).
I prefer to be able to be able to look at the tank without leaning over, and I think taller stands with full canopies look more "majestic". Just my personal preference.
My 55g stand that I built was a little rickety, it did make me nervous sometimes, but it never fell over or even really got close. I had it set up for about 4 years, plenty of drunk people leaned on it, my cat used to jump on top of the canopy, etc. etc., no issues.
My new 105g stand is sturdy as a rock, and I did anchor it to the wall, but it wasn't really necessary. It mostly just helps the tank not "rock" so much when I'm maintaining it, which causes my auto-top off to freak out.
I can barely reach the substrate with my hand without getting on a step stool, but if I'm doing some serious plant trimming/maintenance/planting, then I'll get a step stool. Not a big inconvenience at all really.
Both my setups had/have full canopies, so no real light spillage, but could be a factor if you have a free hanging light. With the right optics, I don't think it would be an issue.
Here's my current setup. Its bigger than it looks in the pictures, the top of the canopy is ~6'8" tall, and the tank is 7' wide. The wallspace the setup takes up including the shelves is 11 feet wide.
Another minor issue is that kids can't see into the tank... I have to get the step stool back out when my nieces/nephews come over.
EDIT: Wanted to also add that the height of the tank makes it incredibly easy for me to do water changes. The bottom of the tank is higher than my kitchen sink drain, which is about 10 feet away, so I can just siphon tank water directly down the sink.