VFS - Walk in without appointment. Anyone done it ?

I've just read this below. i was just about to pay for premium appointment which is about 3500b 

but now im considering this option.

Walk in without appointment

The Walk in without appointment service is designed for applicants who want to pay to walk in to the Visa Application Centre in Bangkok without an appointment. It’s an optional service which means that the applicants are able to:

• Pay a fee to access the VAC on a walk-in basis without having made an on-line appointment or ,
• Attend the VAC on an earlier date than their scheduled appointment or;
• Access the VAC after their appointment time (30 minutes or more) within that same day.

This service will cost THB 1,560 per application and is available in Bangkok only. This can be paid by cash when you attend your appointment at the visa application centre.

Note: If you are applying for a Tier 4 (General) visa please do not book this service. Customers applying for Tier 4 visas are unable to use the Walk In without Appointment service