I don't know how it compares quality-wise to latex offered by other companies, but it seems to be about 1/3 the price.  I don't know if what they sell is soft/medium or firm [no ILD listed]

Does anyone have any experience w/Overstock's latex topperss?  Will it soften my new extra firm mattress?

I just bought this Serta mattress and it's too firm [see my other post] 

Should I try adding this latex topper before returning the mattress?  I have 30 days to return it....

That is a tough question to answer.  Personally 2" would not work for me.  I have 4" over my hard spring mattress, sometimes more.  Some people can get away with 2" toppers.  Do a search on the forum, it's been discussed, it is a grab bag, I have several and some are firm, some are softer.  Mine is 1 1/2", someone else here has bought the 2" version.   I don't want to encourage or discourage you.  Read the reviews at O-stock also.  Some love them, some don't love them.

The height of toppers has been discussed too, we all have different opinions.  What works for me may not work for you.  The height of my toppers is still being worked on too ;-)

Look at the other mattresses they have where you bought yours, if you can change to another mattress would you?  I don't know what they have.  It is a crap shoot I am sorry to say.

Yes I think it would be worth it to try the Overstock latex. Just know that you may get soft, you may get firm, you just don't know - it's a grab bag. If you get a piece you don't like you might be able to sell it here...? Especially if you are lucky enough to get one that is marked as to what ILD of firmness it is, as some have gotten.

If you want to make sure you get a certain firmness you can order from SleepEZ or rockymountainmattress or some other places you can find info about here if you do a search.

If I were you and if you did not pay too much for the Serta (that is, it's not top of the line), I would consider buying the latex topper at overstock.com and if that doesn't work, do mattress surgery on it:
http://www.whatsthebest-mattress.com/forum/mattress-surgery-performing-foam-ectomy-my-englander-mattress-w-photos/6161-A-1.html
Make sure you click ALL to see each post including links to other surgeons' projects.