But yes, at even 50MHz, this is a good buy.
For someone who really needs waveform accuracy though, the DS1000Z platform starts coming apart at the seams if you need quad-channel capability beyond 25MHz.
I plan to use my DS1054Z mostly for power-related measurements and those usually call for a 20MHz bandwidth limit anyway. Pretty much as close to a perfect fit for what I need it for as it gets.
I already have a scope and spending money to replace it requires that certain threshold of improvement is achieved. There are many benefits to the DS1054Z but going backwards in bandwidth goes against the grain a bit. Personal bias? YES! It is my money and I have my criteria for making an upgrade.
This is a bit like a mechanics' toolbox where you may find 10 slightly different versions of a 12mm wrench (angled, straight, knuckle-length, standard length, box, open, pipe, etc.) or socket (wobble, short, medium, long, thin-wall, impact, 1/4", 5/8", 1/2", 3/4" drive, etc.) They are all fundamentally the same tool but mechanics hoard multiple variants because in some circumstances, having the tool that fits exactly right can spare them tons of trouble.
Instead of looking at it as a replacement, you might want to look at it as a complement to cover areas where your current one is deficient. Ex.: you are debugging stuff on a board and suspect it might be power-related but you need your good scope to chase high-frequency stuff. If you had a DS1054Z, you could set it up to monitor the power rails and leave your main scope's channels free for whatever else you need to do.