I ripped out a relatively new Weil-McLain boiler 2 years ago after it shut down on my Christmas day, and again New Year's Day, and about every month it would burn through a flame sensor and every 6 months or so the computer module would crap out. Any alleged "high efficiency" savings was more than offset by the cost of service calls and parts.
This is not to cut down W-M. I have heard good things about their boilers, but my experience was SO bad, I'm a little gunshy. To be fair, I had what was obviously a "lemon" model. Every time I'd go into the plumbing store and tell them what model I had, three other Contractors waiting at the desk would roll their eyes and say "Oh... one of THOSE."
I put in a less efficient workhorse and, neglecting the poor workmanship of the moron I hired to plumb it, have not had any trouble. And actually, have not seen any big change in gas usage, either.
“The keeping of bees is like the direction of sunbeams.” -Henry David Thoreau