Mono OTOH might be okayish for C#, but for instance F# so far has no open source implementation. Also Mono is lacking w.r.t. TCO and GC, so its not even close to a decent VM for functional languages.
But, like so many FF projects: is this the cart, or the horse?
In other words, this feels more like a promotional project for the consulting firm and its pay products than it does a 'real' project. I freely admit this judgement has some external bias; Jon H. has a reputation.
 footnote: (Of course, neither is the linked project... 128 bits for each and every pointer on a 32-bit architecture? Does that mean 256 bits per pointer on 64-bit? Yikes!)
I suggest you think carefully about when HLVM's fat references are a disadvantage compared to the alternatives and why. The real reasons are not at all what you're thinking (or what I thought for a long time).