That's the poncho I use. I bought it mostly due to its length (I'm quite tall).
I looked for one on-line for my son - who is even taller, but I couldn't find out. I assumed they were no longer available.
To be honest, though its been used a lot - as a poncho - and it is very well made and has taken the use/abuse well. As with any poncho, on hot days, with exertion, it can be hot, but not so bad as a rain coat would be.
I've never tried out the bivy capability. I can't imagine wrapping myself in non-breathable nylon for very long. I'd come out soaked.
If you're looking for more of a bivy I might suggest something breathable.