I bought the £20 Memory Map app for my girlfriend's Iphone 4, largely because I have a vast # of MM QCT maps; 1:50k for all of UK, etc, and there is a lot of QCTs on P2P, torrent, etc. including the current 3 CAA charts joined into one.
As far as I can tell the
free MM app doesn't accept any QCT maps.
The £20 app appears to download street maps around your current GPS position but MM do not reply to any emails so I have not found out the map coverage limits. I don't know what the entitlement there is... But it runs all the old QCT maps OK, including O/Survey ones, and they get uploaded to the Iphone via a WIFI "ftp server" feature which you get on the £20 app.
It is a horrid clunky app but there is no other way to run QCTs. Somebody else developed a QCT viewer but IIRC MM blocked Apple from accepting it into their shop.
It runs the MM CAA charts OK.
Whether the Iphone does what you need is an "individual decision"
I have had to be very careful to not tear out my remaining hair because while the thing is wonderful up to a point (the point having been carefully defined by the Apple Politburo in a special plenary session to determine "privileges for the great unwashed") it has a lot of
very irritating limitations. The GPS is excellent on the ground but I wonder how long it takes to get a fix if turned on in the air; also there is no way to have the GPS enabled and GSM disabled so there is always the risk of avionics interference.