Currently in theatre, from what I've seen, the only people wearing them that could possibly argue value for them are aircrew and MERT teams - who to be fair only wear small ones and even then only affixed to their UBACs not MTP. Every squaddie I have seen with any form of patch id has always been on their Osprey, never on MTP - again, it is usually the designated ISAF patch with a small afghan flag and maybe a blood group.
The only chompers wearing custom patches with all manner of useless ****e on them, including Union Jacks in a vast array of tones, ZAP numbers, Ranks etc are ironically those personnel least likely to go outside the wire. I'm ashamed to say a lot of Techies think it is "cool" - it isnt, you look a c**t. There is no uniformity to the info on these patches and as such they look a bag of ****e.
If you want one made by the jinglies with your name, service, section on it etc for your bag then - a bit cabbagey -but fine, if you are not likely to be engaged by enemy fire, IED's etc then don't bother with the MTP ones, you'll look a right t**t.