Following up on my own posting with more information...

This morning, I got a third consultation from Stephen
Frederick. Stephen has been installing and repairing gutters
in the Boston area for more than 25 years and comes highly
recommended by friends of ours and by everyone on Angie's List.

The most important thing he told me is that the biggest risk
mentioned by the other companies -- water leaking behind the
gutters and causing the fascia boards to rot -- is not in fact
a risk at all, because my fascia boards are covered by
aluminum. Neither of the other two companies mentioned this.
Either they both intentionally misled me about the risk of
rotting fascia boards, or they were both too clueless to
understand that it isn¢t a risk when the boards are covered.

Stephen also said that none of my gutters need to be replaced
("I hate to say it, but those gutter cleaning companies don't
make a lot of money cleaning gutters; they make their money
//selling// gutters") and that he only sees them pulling away
from the house slightly in one place, which he said he could
repair for about $100.

Stephen strongly recommends against gutter covers for two main
reasons:

1. They don't really keep everything out of the gutters.
They may keep enough of the big stuff out to prevent the
gutters from becoming completely clogged, but they let dirt
and small stuff get through and build up at the bottom of the
gutters. This has all sorts of negative ramifications, e.g.,
slower water flow through the gutters to the downspouts; extra
weight on the nails / screws causing the gutters to pull away
from the house; providing a breeding ground for mosquitoes;
etc. Furthermore, in a good ol' New England deluge, the
covers don't let the water into the gutters fast enough and it
comes pouring over the side.

2. The supposed lifetime warranty applies for as long as
the covers are attached to the house, but what they don't
mention is that they put screws through the bottom row of
shingles when installing them. When you replace your
shingles, the covers have to be removed; say good-bye to your
warranty!

I called New England Gutter Kings and asked them to fax or
email me a copy of the full warranty on the covers, since the
informational packet they gave me contains only a "summary" of
the warranty. They said they would email it to me "right
away," but it never arrived. This could have been a simple
email transmission problem, or perhaps it was a passive
aggressive attempt to prevent me from seeing the full warranty
before paying them to install the gutters.

It looks like I'll soon be another satisfied customer of
Stephen Frederick.