Ok., its true, the software I used the longest is the one I liked the best
but
I'd hope that is because it really was the best. The three mentioned
systems
I've used are Incases' Theda/Autoboard, Mentor Boardstation, and Cadence
Allegro. Here's a brief recap of what I remember.

  Mentor. I spent three months learning to use & working with Board
Station.
Basically I'd have to say "you can't get there from here" or if you get
there,
by the time you get there you've forgotten where you're going. Mentor can
certainly be used to create PWB data but it always seemed like a lot more
trouble than was necessary. Where I used it we were doing mostly manual
routing and it had an overlay for a large consumer electronics company that
shall remain nameless. It's possible that in another context it would be
easier
to use. One good feature it had was the way it tied the component data base
and schematic/pcb libraries into the layout and schematic capture program.
It creates lots of files in lots of places which, unfortunately, aren't
readily editable
to achieve desired modifications. One point in their favor is that their
users e-mail
forum is [the last time I checked] open to anyone; no passwords, secret
handshakes,
etc. Some ECAD software companies will barely let you into their web site
without a
blood oath or something. Mentor can be tamed but it takes time and
ingenuity. I even
know people who really like it.

 Allegro. I've been using Allegro for 8 months. Basically it's a good CAD
system and
not terribly hard to grasp the basic operating principles of. Unbelievably
though,
once you exit a command, there is NO UNDO! If you never make a goofy
mistake
or have an unexpected outcome from a command, more power to you. I just
find this to be
a serious flaw. We've also had problems with the 274X Gerber outputs though
I'm not sure
how much of this is Allegro and how much is the fab house. This was
discussed on the
forum last fall. Their release of the reasonably functional "Allegro
Studio" with schematic
capture, layout, and library utilities for ~ $10K  will hopefully be seen
as a challenge to meet
by other upper tier ECAD software companies. If you choose the Studio
Package, make sure it
has all the functionality you'll need in the near future. Some features are
only available in the
Designer or Expert packages. Of course, you can always upgrade.

 Theda. I used various versions of Autoboard for 7 - 8 years. I miss it. My
favorite feature of
Theda is that all or part of a database can be written to ONE text file,
edited, and used to regenerate
the database. This feature is very helpful for revisions, padstack
substitutions, script writing, data
extraction, etc. Most of the time, when I needed to do something on a
layout, Theda had several reasonable
ways to do it. A lot depends on what your current and future layout needs
are; but as an example, Theda
will create a negative split voltage plane very easily and automatically
tie all the same net lands and vias
into the plane. In Allegro, it's "coming in the next revision" and in
Mentor I honestly don't remember if it could
do this or not. Theda is also absolutely "what you see is what you get."
Allegro is mostly WYSIWYG and my
experience with Mentor is "what you get is what you get." Reuse of
circuitry is fairly simple; capture what you
want as a module and (if it's backed up by the current schematic/netlist)
drop it in the new design. In Allegro
this feature is coming soon and in Mentor, I believe, they're looking into
it. The worst thing you could say about
Theda is that it was once owned by ComputerVision but that's long ago and
far away.

 Gerber PC800. OK, Just kidding........

 All of the above is my PERSONAL OPINION as a user. A lot depends on what
your current and future
design needs are. You can do a perfectly good job with a relatively
inexpensive package like Protel
as long as your design needs don't exceed its capabilities. By the way,
does anybody know why there
is no PCD Magazine Benchmark this year? It had its flaws but basically
seemed like a really good idea.

Tom Martin
Sr. Printed Circuit Board Designer
TV/COM, Intl.

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