I use them a lot for sales through my website and also less frequently on eBay as I offer both Sendle and AP options. As another poster has experienced 95% of the time it is Couriers Please that collect with the 5% being Fastway. 

Pros

1) They collect from your home or you can drop off at many drop off locations (have yet to try that option though)

2) They are cheaper than AP in most cases except extremely rural locations

3) They are quite relaible in the delivery of items

Cons

1) Only email support is available

2) Although they offer insurance in reality it does not exist. Twice I have had issues, once admittedly was a parcel sent to me and not packed well at all which they refused insurance on (understandable in this case but they use every tactic possible to worm out of it) and another where the parcel went AWOL and I actually had to do the detective work and found that it had been wrongly left at an address next door. When trying to get them to investigate whilst it was lost they refused insurance again or to take responsibility or even really investigate it until I mentioned the Postal Ombudsmen.

3) They can be unreliable in picking up the designated day and in around 30% of cases collect the next day. Not ideal if you have a busy life where you cannot or are not at home much.

Overall I think they are OK if it is Couriers Please.