Over the years I have owned and camped in numerous conversion vans. I've never lived in one though but I wouldn't think that it would be too uncomfortable as long as you lived a minimalist lifestyle. The big problem would be the facilities but my boat has an answer for that. It is a very small chemical toilet. It sits underneath a box that looks like it is a built-in footstool.
Living in a climate where the temp drops to -20 below there are times where you would need some sort of heating. A small catalytic heater could help but would be dangerous unless you also have a CO detector. Perhaps a small furnace from a travel trailer would be a better solution (keep the CO detector to be safe).
What besides space would you be missing? Today you have cell phones, LCD televisions, wireless internet. Almost anything that plugs in can be had for 12V and inverters are available for those things that can't be.
I went to school and emerged debit free. I lived in my parent's old house that hadn't sold yet and only paid utilities (that was a big help) and relied on a part time job for income. I got the GI bill and was lucky enough to win a grants for my text books and other school related expenses and even got some money for tuition. While many of my fellow students emerged with huge bills for student loans, I graduated with zero debit!
Was it worth it? Hell yeah. I only had to concentrate on the future and was not haunted by the ghosts of the past; all those ghosts named "Bill".
I can say if I had to do it again and if I had to live in a van to emerge debit free; I would not think twice.