With stuff like web sockets/Web rtc /whatever new awesome sauce is out today a lot of that has changed, but that's still really the same spirit of ajax anyway, just with actual persistent connections instead of hacking it with long polling.

You can write a shitty system regardless of paradigms used.

You can write a beautiful system even with painful primitives.

All it comes down to is how much time and talent you're willing to invest, which is admittedly a cliche and non answer, but true nonetheless.