I had snapmarks for a while, and lost them when I had to exchange my machine. They were very handy, and I’d love to have them back, but honestly they didn’t let me do anything I couldn’t already do; they just made it a little bit faster. So I’ll be happy when I eventually (hopefully) get them back, but I’m not handicapped in the meantime.
There have been some great ways posted in the forums that you can use to nail down your registration without having to use trial and error. If you take some time to read through the Tips and Tricks section you’ll get lots of great ideas, depending on the types of project you do.
I use a lot of jigs, myself:
You can also make a crumb tray ruler for exact visual positioning (there are a lot of these; this is just the first one I found):
And to nail it down even more, you can use these to make sure your tray is always in the same place: