I'm a bit mystified by all the responses urging not to do it...
As a PV installer we size systems as close to 600V DC as we can. That's normal practice, as it minimizes losses and makes the most economic sense. All the equipment involved is of course rated at 600V, and this does not mean it will fail at that voltage, it means it will continue to work normally at that voltage. Insulation values of 600V rated wire and other supplies is several times beyond the rated voltage (they have to pass hipot testing with a factor of 2 or 3x rated voltage, forgot the exact multiplier). In short, there's nothing wrong with going with such a high voltage. If the components are rated for it code will allow it.
Having said that, this assumes you know what you're doing. Others are correct that this voltage can absolutely kill you. Then again, so can much lower DC voltages (getting zapped by DC is worse than AC). It helps safety-wise to float the DC side, so you have to actually touch both terminals to get zapped (the inverters we use are transformerless, so there's no grounding of the negative lead, a very good thing IMO). Also, and that is very important, string size needs to be such that you stay under 600V DC open-circuit voltage (unloaded) for the absolute coldest temperature that can reasonably be expected for your location. Going over 600V will set a flag in the inverter's permanent memory before it blows (for a 600V rated inverter), and you can wave bye-bye to the warranty. For our climate, with -35C as the minimum (and that means I use -40C for string calculations), the MPPT voltage of the string at normal temperatures usually ends up somewhere in the 350V - 400V DC area.
-RoB-