No True Bypass sorry.  I have an M13 which as you may know has both True Bypass and DSP Bypass which incorporates a measure of buffering.  I use my M13 in 4CM configuration which rules out using True Bypass anyway.  There's little if any noticeable difference between the M13's True Bypass and DSP Bypass when working in a live environment in particular, and if the HD500 had True Bypass, I'm fairly certain the result would be similar to the M13 - i.e. no noticeable difference.  True Bypass is all well and good in certain situations, but bearing in mind how good DSP Bypass is these days it could be argued that it is not really necessary.  True Bypass would have required additional relays being fitted to the HD500 and of course this would all have added to the cost.  The main idea behind the HD series is for them to be High Definition AMP and FX modellers rather than just stomp FX modellers like the M13 and for users to have the benefit (particularly with the Variax or new JTV guitars) to be able to turn up at a live event with just a guitar and say an HD500 and maybe a flat response powered monitor and to be able to pretty much cover any sound.  What I'm really saying is that whilst you can use an HD unit for just FX I would perhaps see the M13 as the better option IF that's all you want it for.

Nick