I think a mixed border would be the way to go, rather than planting all one thing. More interesting visually, and if one thing happens to become infected with disease or dies for other reasons, it doesn't look as funny/like there's a big hole left.

We moved here 2.5 years ago, and priority one was creating more privacy in the backyard. I did a lot of research on fast-growing evergreens. I do have to warn you that "fast-growing" often means growing, eventually, to monstrous heights. :)

I think my top recommendation for you, considering the "not to monstrous heights" criteria, might be Silverberry/Eleagnus. I have one along our fence. It's an evergreen shrub, and I think the top height I saw for it was 15'. I planted one a year ago, small, and it's just about doubled in size (still only a couple of feet tall...it was small when I planted it). It's worth considering as part of a mixed border, for sure, but I don't think I'd like a whole row of them. They can tend to look a little wild. Definitely not a formal look.

I put trees along our side yard, and I went with the three that had the fastest-growing reputation. Planted them all about the same size, and let them race. :) Those were: Green Giant Arborvitae, Japanese Cryptomeria (Yoshino), and the dreaded Leyland Cypress.

And the winner, after 2.5 years, by a landslide: Leyland Cypress.

They were planted as 2-3 ft. tall specimens. I have a couple that are pushing 8 ft.

You have to give them room horizontally, as they can reportedly get very wide (although I've not witnessed this locally...). Some sources say 25' wide. Because it was extremely important to me to get a fast screen, I have them planted on about 8' centers. We'll see. I may be sorry, but then again that was the spacing recommendation for a privacy screen from UT Ag Extension Service, so maybe not.

Leylands get bashed a lot because they are supposedly prone to disease. Another reason for doing a mixed border, in case you lose one.

I would go with a mix also. That way you have flowering plants along with the plain green. And like was said by connie, if one gets sick, it will not kill out the whole fence.
Search the web for flowering fence.

I planted a row of leyland cypress to create a screen on a section of one side of my property, spaced them 10'. They were 1 gallon trees when planted and are now pushing over 3 feet and really growing already this year, with not much growth last year. They were planted the previous fall. I expect much growth from them this year.

I am not sure why they are considered the "dreaded" leyland cypress???

I also have several arborvitae on the front entrance that were there when we bought the house that are growing nicely as well. Nothing fancy about either one, just green and both are supposed to grow and fill up fast.

"I think a mixed border would be the way to go..."

I second that entire paragraph!

Elaeagnus commutata (Silverberry)

Avoid the invasive relatives:
Elaeagnus angustifolia (Russian Olive)
Elaeagnus pungens (Thorny Olive)
Elaeagnus umbellata var. parviflora (Autumn Olive)

As for E commutata, Dirr comments that he "doubt(s) whether it would survive (long term) in (our) humidity and heat" and lists it's upper hardiness rating at zone 6. Apparently the climate here weakens this species and makes it susceptible to various pests and disease. So, do your research before counting on this one, and let me know if it does OK long-term (if you remember after a few years of trial)!

Green Giant Arborvitae, Japanese Cryptomeria

Some great choices!

Leyland Cypress

I'd pass on this one. Every day I see more of these suffering and dieing from bagworms. This species is just plagued with them! It also commonly suffers from a number of other ailments. IF it survives these (highly doubtful, long term), it has the potential to grow to extreme proportions. Here's one that's about 120' tall with a 3.6' diameter trunk:

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Millingtoncb, if you want to know why I called it the "dreaded" Leyland Cypress:

1) Go to the conifer forum.

2) Tell them you are thinking about planting a row of Leyland Cypresses.

3) See what happens. LOL! :D

4) You will likely see the above picture again.

...or just look around for an evergreen screen that appears to be dieing out and turning brown. Chances are decent that, upon closer inspection, you'll find it's a row of Leylands with bagworm cocoons attached.

I understand the bagworm thing, but if they start appearing, you just have to stay on top of it, I get the bags, but just go out early and take them off and dispose. I realize this is not a fun task for dozens of LCs to maintain.

I have seen LCs in the state that brandon describes above and I have seen perfect screens that are 15+ years old. Most of the browning screens are probably not taken care of and monitored for bagworms and controlled, just speculation of course. Mine are young, but there are a few that are at least 5 years old and are absolutely beautiful, built into a screen along my ditch/property line. I watch for bagworms and any insects for that matter and when needed, use a moisture meter to add water when needed in hot, dry months. I also give a ring of compost around the tree in the fall, and sprinkle osmokote around them in the spring. They look great so far

I do not plan to get a lifetime out of these trees. I guess if your expectations are in line, then no harm no foul.

I guess the big question would be why choose a plant that is not as good looking (at least in many people's opinions), requires significantly more work, is much more prone to bagworms AND other pests and disease (that may not be as easy to prevent), and will require one heck of a tall ladder in just a few years to be maintained, when there are better choices. If you're happy with Leylands, then by all means keep them or buy more, but I just don't understand why anyone would.