Application Sent: 29 January 2015
Application Received: 30 January 2015
Payment taken: 5 February 2015
Email confirming receipt: 6 February 2015
Acknowledgement letter received: 16 February 2015 (dated 5 Feb)
Approval letter received 21 February 2015 (dated 15 Feb)
As an added bonus, on the same day that I received the approval letter, I also received a letter from my local council starting 'Dear Future Citizen,' informing me that they booked me onto a citizenship ceremony on March 18th!
I was a pretty straightforward app, Tier 1 the whole time prior to ILR, same address, same large employer, nothing interesting on the travel front, etc.