Had a short "casual business" trip to India (BOM) recently.

Here's my experience. EU passport holder.

(1) Applied through online portal. Paid with CC.

(2) Response email granting visa came in about 24 hours. Simple email printout

(3) Check-in/Gate agent asked to see e-visa confirmation

(4) At arrival in BOM entered the immigration hall. There's a small glass enclosed section with Counters #1-8. That's where e-visa arrivals are processed (as well as diplomatic passports, or other special situations), not in the main section of the hall. I actually walked right by it and thankfully a staffer directed me there before I wasted too much time in the queue.

(5) Gave passport and e-visa confirmation to immigration officer. He also asked to see my boarding pass (showed him mobile b-pass it was fine). Took photo and fingerprints. No questions. That's it. Took about 3 minutes and there was no queue whatsoever. Faster than any other line in the immigration hall.

(6) On departure, they just asked if I'd come in on e-visa and that was it. Took another photo. Stamped passport and sent me on my way.