Upgrading to business class on Vietnam Air worth it?

Flying to Bangkok and received email promo stating faster immigration clearance but couldnt find any further information about this.

It certainly pays to ask.   ..and again, if the queue is empty on business class!

I got it for free, just by being in the right place at the right time

..after (of course!) I diligently packed light, then given an extra 30 Kg free...       :mad:

*  yes, clearance is (much) faster now