I only use them if I expect to be in that area again.  Otherwise, no use for any of them except the consulate and maybe the tower to grab that one last resource.

I occasionally use the Hightower. Other then that no. Other people seem to like Wardens but I usually clear out all the monsters weak enough to be effected by it. Coltraps are too late game. Stables affect too small of an area. The chances of actually fighting anything beside an outpost is way too unlikely so I never build the stat boosting ones. You're much better off defending a city then using any of the defensive ones. I might start using the consulate because in LH growth has been slowed.

One thing I would love to see as a outpost upgrade is roads. Allow us to manually spawn roads to outposts. Instead of having a tech do it to all of them. This would just be a much better system.

The point of outposts is to spread your territory to claim resources. For Outposts to serve any military purpose you actually have to be to able to hinder enemies with them. Firstly making coltraps appear earlier on the tech tree would help a lot. Changing the Abbey to significantly reduce the cost of offensive strategic spells would also help. The high tower could also have a vision of 6 to show incoming armies. With these changes it would be worthwhile to build outposts on your borders to slow invasions.

I rarely use them except for the range extender because training a unit is always more valuable. 

My two cents:

Fewer better upgrades (combine existing ones). 

Passive leveling based over time where  the distance to your cities comes into play.

I use High Tower to expand ZOC to grab a resource or to connect cities.  Outposts are too flimsy to risk investing much in them, warden is unreliable, especially near wildlands,   Consulate is kinda cheap, and the other stuff is boring.

I think the problem is mechanically, it's micromanagement for the most part.  I think the System would work better if outposts had levels and the upgrades were based off of level.

My suggestion: Outposts have three levels beyond initial outpost, unsure what the cost to upgrade should be.

Each level of outpost provides some benefits, lvl 1 outpost keeps "weak" monster groups out, lvl 2 keeps "medium" out, lvl 3 keeps "strong" out.  Also makes it require that level of strength to take the outpost from enemy troops.   Outposts would provide other bonuses (military related- dump consulate/stables/abbey)

High Tower effect would come in on lvl 2

Caltrops on lvl 3.

The effects of the abbey should probably be handled by a world wonder instead of a fortress upgrade.

The effects of consulates- I could see that being a Krax bonus, outposts increase growth slightly based on fortress level (but does not stack)

That works?  I didn't think it would apply to stationed units, so I didn't actually give it a try.  If that works, that'll really help me.  I'm going to give it a try.

What happens if a city snakes to an outpost that has the combat/movement bonuses, etc?

I had it happen once while building my own 'superhighway' as Darxim calls it, and I noticed that the improvments (specifically stables) moved into the cities' list of buildings but honestly I didn't do much testing as to how it works, just wrote it off as weird and moved on.

EDIT: well that was interesting. Did some testing with Pariden and arcane monolyth and the basic attack/defense upgrades and it seems that if you snake to an outpost after building upgrades in it, everything works fine. the upgrades are in the list for the city as one of 'its' buildings, but in the outposts list too so you can't build them again. If you build an upgrade there after snaking to it it only appears in the list for the city, not the outpost and so you can build it again, an infinite number of times.....

EDIT2: also, even though the building (eg, armory) is listed as a building that the city 'has' if you snake to it (possibly multiple times if you snake to multiple outposts, and the bonuses stack ) the effect is still only local to the outpost. Also stuff built after you snake has no effect, at all (I forgot to check that before my first edit)

Final note: Snaking only occurs (the outpost becomes included in the boarders of the city for the porposes of ZoC around the city, including the healing the land effect) if the outpost has at least one upgrade, or you start building an upgrade once snaking could occur, untill then the city won't expand it's boarders or put the graphical fence around the outpost.

This. This would make me use the outpost upgrades more

Frogboy,

If I may suggest please consider creating a similar upgrade path for outposts like you already have for cities.

Picture this, you build an outpost and then upgrade it. the first upgrade would make you choose between 3 options.

Offensive: Arrow tower, Mage Tower, ect...

Support: increase movement, increase growth to towns, heal 2hp per turn to any friendly unit in range, ect...

Defensive tower: decrease enemy movement, reduce damage dealt by enemy, reduce attacks from wild life, ect... 

Would be cool if they could act as fortresses as well, so you could garnisson troops there. I like the current upgrades, but they could've been extended upon with walls upgrades (defense bonuses for the garnisson) etc.

I use them a lot. But perhaps it's because I like to play with Procipinee. In fact I do exactly the same as Draxim said:

I disagree with the idea of giving outposts their own build queue. In my opinion it makes a lot of sense that the city has to build outposts upgrades.

I also use the current outpost upgrades quite a lot, especially since I've stopped founding so many cities

It would be great, though, if the build outposts trait could be applied to another unit (e.g. scouts or engineers) to avoid the pioneer cost...

I use the upgrades fairly often.

I use stables along my major thoroughfare early, and slowly upgrade all of them to stables by end game.

When planning location of outpost, I usually plan ahead keeping in mind its ZOC with the high tower, depending on tough monster locations.

Use the attack/defense building on a more limited basis; for help taking down a near tough monster right on border of ZoC, and sometimes if I park an army in the outpost's ZoC near an enemy if the outpost is also a chokepoint.

Late game I'll usually get consulates up and running on a per city need.

Caltrops I very rarely build, although every now and then they are nice, when enemies are trying to run armies past my defending army, and defending army just doesn't have enough moves to get them all in one turn.

Wardens I build on a per case basis of near monster lairs, especially early game.