I agree that Caltrops has its drawbacks, all I'm doing is making the qualitative argument that against Ichorid, the first few turns are the most important.  To me, the longer a game against Ichorid goes the more of a shot Stax has at winning.  So if I can weather the first few turns then I'm already on my way to winning. 

To sum up:  Ensnaring Bridge:  Does nothing against onslaught first few turns.  After that it is solid.
                  Caltrops:  makes Ichs, Moebas, Dryads irrelevant.  Fails to kill tokens without multiples and if opponent
                                can Dread Return through lock pieces can hit you with a sick swing.

A highly conditional play, if the match hinges so much on Bridge from Below then throw your own welder into the caltrops.

I don't want to drag this out, depending on someone's build, its a judgement call on when you believe you are the most vulnerable.  I feel its early, prior to many of the locks coming down.

Ensnaring bridge will work well but it is a question of how quick your opponent goes off.  In the first three turns, unless you have a hand full off moxen, you are not going to be able to dump everything out of your hand.  With a non workshop hand it is very plausible you are only casting one card a turn. 

So early game I see caltrops as more effective, slowing him down, mid game still being able to lock out tokens and Ichorids with a second Caltrops.  And as for a dread return for a golgari troll or something, a single permanent is easier to deal with than the multiple small creatures they have.  Sacrificing 3 creatures to bring out 1 plays into Uba Stax gameplan.

Has anyone thought about Caltrops as a sideboard option against Ichorid?  Reason being, Caltrops stops all Ichorids and Narcomoebas and in multiples it is GG.  Caltrops is also not a dead card against fish and G/R beats and other random.dec(s)  that are out there.

Another nice side to caltrops is it can be workshopped (is an artifact) so, unlike slice and dice or pyroclasm, it functions through your own soft locks. (and welderable)

If an Ichorid player gets rid of your initial leyline, then the matchup goes back to a preboard situation since you have no alternative to hardcast another.

Just for clarity: I am not saying to board this in as a substitute for Leyline or remove Leyline from the sideboard. Leyline helps in other matchups i.e. Flash and the mirror that makes it indispensable.  I am talking more in regards to the side board discussion on page 1. 

For Ichorid: It was mentioned before that you would sideboard the following: -4 Crucible, -4 Uba, -4 Smokestack and replace with
+4 Leyline, +4 Powder Keg, +1 Karn, + 2 Sphere, +1 Words of War

Powder keg was referenced to kill opposing zombie tokens, as well as Warren's tokens.  However outside of tokens powder keg takes time to kill anything else off, and in regards to Ichorid it is the quick clock that an Uba Stax player is most concerned about.  Caltrops begins to work immediately and you won't blow up any of your own artifacts in the process.

Caltrops does work both ways.  It will kill your welder if you swing but against Ichorid a sacrifice like relying more on Barbarian Ring in order to reduce the opponents tempo is worth it.