Is it worth the extra money to buy a convection oven?  I am talking
about a regular oven, not a microwave oven.  If the answer is that a
convection oven is worth it, recommending a good choice would also be
helpful.

I'll leave the recommending to others, but I am crazy about convection
ovens. When mine broke down and we could not afford to replace it, I
was very sad. I loved that oven. Returning to cooking with the old
conventional oven is a big step down.

All regular ovens are convection ovens. 

It is likely that you are reading looking at an advertising gimmick,
like when corn oils advertise themselves as 'Cholesterol Free' corn
oil couldn't possibly have it to begin with since cholesterol is only
found in oils made from animal fat.

elids,

The term "convection oven," as used in the appliance industry, refers
to an oven with fan-forced heat. It's definitely no gimmick.

yup I just looked it up, looks like you are right pinkfreud. The term
though is a misnomer, convection refers to the way in which heat is
transmitted, so although my original comment was not incorrect,
because they add a fan to the oven it is not a gimmick, it is a
misnomer.

I don't see where the misnomer is:

Convection
http://www.answers.com/convection

Actually, there's more to it than just blowing around some hot air:

FROM: Better Cooking Through Convection
http://www.taunton.com/finecooking/pages/c00042.asp
Besides the excerpt below, this is a great page for those that want to
know more about convection cooking.

..."Not all convection ovens are "true convection"
The extent to which you get these marvelous results depends a lot on
the particular convection oven you're using. The best -- and most
efficient -- convection ovens blow heated air into the oven cavity.
This means they have a third heating element (in addition to the usual
top and bottom elements in a radiant oven) located near or around the
fan in the back of the oven. This element heats the air to a uniform
temperature before it enters the oven cavity. In many ovens, the third
heating element is covered by a baffle, or a panel, which channels air
sucked in by the fan past the heating element and back out into the
oven.

The appliance industry generally calls this type of oven "true
convection," "third-element convection," or "European convection"
(first popularized in Europe), so these are the terms to look for when
shopping. In an effort to distinguish themselves, however, some
manufacturers have come up with their own names. Dacor, for instance,
calls its technology "Pure Convection" because its third-element
convection also uses a special filtering system that prevents odors
from being transferred from one item to another cooking in the same
oven..."

I hear that "convention ovens" are great, but I too have always
considered this a misnomer, only slightly better than "organic food".
As Elid mentioned, all ovens (except microwave ovens) are convection
ovens. These things should properly be called "Forced Air Ovens" or
"Forced Air Convection Ovens" or something like that.

While my sister loves her "convection oven", beware of some
exaggerated claims. I remember going to her house for Thanksgiving.
She told us the turkey would cook in half the time. I was skeptical
since forced air is not going to speed up the diffusion of heat inside
the turkey, which is what makes cooking something thick take so long.
She had a nifty built in thermometer with digital readout. I watched
if for a few minutes, took the derivative, extrapolated and told her
the turkey would be done two hours later than her planned time, which
is what happened. This exaggeration is probably attributable to an
over eager sales person rather than the oven manufacturer.

In the UK we call them Fan Assisted ovens.

I would not consider buying a non fan assisted oven

IME they cook faster at lower temperatures

Fan Assisted Oven is a much more descriptive term. Everyone who has
ever expressed an opinion to me loved his or her fan assisted oven. I
don't doubt that they cook faster for moderate sized items where the
cooking time is all about heat transfer at the surface. My point was
about something very thick, like a whole turkey that takes many hours
to cook. In that case, the surface warms quickly to the tempearture of
the oven and then you wait for hours for the heat to diffuse into the
center. Forcing the air is no help in that process, except for the
time saved at the very beginning.

@kottekoe-ga 

I think we all followed your point - it is a good one.

One can speed things up using steel skewers 
- and putting things on racks - but your point holds.

Convection ovens are certainly no "gimmick". I have been cooking
professionally for 18 years and there is a definate difference between
convection ovens and conventional ovens. "Unlike conventional radiant
(also called thermal) ovens, convection ovens have a fan that
continuously circulates air through the oven cavity. When hot air is
blowing onto food, as opposed to merely surrounding it, the food tends
to cook more quickly. A short version of the scientific explanation
for this is that moving air speeds up the rate of heat transference
that naturally occurs when air of two different temperatures
converges. To help understand this, consider wind chill: When cold air
blows against you on a blustery winter day, you feel colder more
quickly than you do on a windless day of the same temperature."