I have been using the Serenity in combination with the Gatewood since about March '08. I agree that it is an elegant design and multi-optional. I have not sent my harness in for retro-fit of a D ring. I just seared a hole in the webbing "pocket" of the top strap. I push the end of my 45" aluminum pole (assembled from parts available from Quest Outfitters - I don't hike with poles) through the pocket, then through the grommet in the Gatewood harness. It seems to work well, although I should perhaps have the D ring installed. Another option might be to install a small grommet in the top strap that would serve the same purpose as my seared hole.
I don't really mind the somewhat confining nature of the Serenity, nor do I notice the netting on my shoulders when sitting up. The loss of interior space is a downside, but then, it IS an 18oz tent afterall! On very warm humid nights (typical summer weather in the Midwest) with no chance of rain, the Serenity is superb. Much less confining than a bivy, complete bug protection, decent ground protection (esp. with a polycryo or Tyvek ground sheet), complete ventilation, easy entry/exit and extremely light to boot. What more could one ask for? I have not noticed any stress or unusual fragility of the netting. I sewed my own stuff sacks for the Cape and the Serenity, and I use Ti stakes for a very lightweight package. Coupled with the Gatewood Cape, I think they comprise the ideal multi-use shelter/raingear. Thumbs-up all round by me.