This morning I typed out a very long response and then the forum went down:sly:, but basically it comes down to issues I've encountered on other devices. I'm sure it works fine for nexii, but it had issues wiping on one of my previous devices (i got to deal with a lot of support questions from it) and it bricks misc partitions on my current one. They had to pull support for it. Overall just a bad taste in my mouth.
Also, its another way to steer new people clear of ROM manager until they learn to do things manually via recovery and fast boot. I always suggest staying away from apps that automate recovery functions. They tend to cause more issues than they are worth for those who are new to rooting.