I was there a couple of months ago and have been twice altogether. No problems, although get there as early as you can. There can be quite a queue and you need to wait in line to hand over your paperwork and get given a number before waiting again to be called for your "interview".
Although people aren't served exactly in order, there is a loose correlation between the time you arrive and the time you get seen.
You MUST have all your paperwork in order though or you'll be sent to the back of the line or sent away! If you don't know what the issuance fee is (£68?), you should double check you've done everything - you have to pay it at a bank BEFORE you go and bring the coupon as proof. You need a load of other random stuff too - return envelope and photograph etc. Note when they say they need the photo to be of a certain size they mean it! I saw loads of people being sent back to get new ones!!
I was there (both times) for around three hours. The interview took around a minute both times...
Hufty.