Keith, there are indeed more options available recently due to advancements updates in the Tooling API released by SFDC in the months since the original post was made...
...but they're probably not exactly what you're looking for.
Personally, I've recently shifted from an eclipse-based workflow to one built around SublimeText. Although this is largely due to my recent MacBook Pro purchase and the large and growing community of support around developers using OSX as their primary development environment, a big part of it has also been a reduction in the amount of SFDC development work I do on a daily basis. My reliance on he eclipse-based system fell as I needed less and less from my IDE for SFDC work...
All that being said, there are a couple of really interesting options that I think are worth considering:
MavensMate - Joe Ferrara & DoubleSharp have been leading
an active github developer community with a lot of commits over the
last year and quite a bit of functionality being added and bugs
being addressed. Not sure if you're ok with the base $70 license
fee of SublimeText (even though it's really just to get rid of
the nag pop-up, you can use it fully functionally to figure out if
it's a good fit), but if you can handle that, MavensMate seems like
the lead contender since SFDC abdicated the throne.
BrainEngine - This one was mentioned in the previous
thread you reference, but it too has seen significant development since that
original post. It appears to have a significant amount of commercial backing
and is quite a polished final product. They have a yearly license fee for the
Developer version which appears most comparable to SublimeText + MavensMate,
but it's a single tool suite so it may be easier to manage the change in your
workflows only having to take on one new toolset.
Cloudsole.com - This one is still in .1 release, but it's existing
functionality looks pretty impressive. There's a recent blog post I'll
link to in the comments since I don't have enough rep to post more than
two links in an answer, but it's built on top of heroku and appears to
at least have the deployment aspect down (not surprising since it's a
heroku app itself) and a pretty decent compliment of IDE tooling already
completed. It's also open source and hosted in github so any updated
features you needed right away could be added in if you wanted to become
active in its development community.
Of the three, MavensMate or BrainEngine appears to be the most mature, fully featured IDE's available built on top of the Tooling API, and from the (lack of) activity from SFDC in anything but Tooling API updates, your best bet may be to join the MavensMate / BrainEngine community.
