I came across the Quattrimus site which has both CM9 and AOKP Ice Cream Sandwich ROMs for the LG Vortex and other LG Optimus One phones. The ROMs are in the beta stage so there are a few issues. Most notably, the sensors don't work (e.g. screen does not auto rotate) and there is a low mic/speakerphone issue. Also, international data roaming must be enabled for data to work. These seem to be the same issues that affected the CM7 ROM. More information can be found in this thread.
I loaded both ROMs on my Vortex and used them for a couple of days. While I only tested for a short time, the performance and functionality of both ROMs was very good. If the sensor and mic issues get resolved, I will definitely keep one of these installed.
The developer is also working on a Jelly Bean ROM. I'm keeping my fingers crossed,
