Both excellent phones, in my opinion (the best of Nokia, and in my mind, therefore the best in the market) I would say that the E66 and E71 are so evenly matched that the most important thing you need to ask yourself to decide which one you want is whether you need a keyboard or not.
Feature wise, the E66 has an accelerometer (E71 doesn't) which lets you rotate its screen easily, and perform gimmicks (like silencing an incoming call by picking up the phone and putting it back face-down). It (E66) also has fancy-looking (fade in) transitions when navigating from one screen to another (so there may be some minor software differences between the two).
I must warn you about a serious flaw with the E71, though (obviously, I only discovered this after I had started using the phone): the antenna is in the base of the phone, and is overly sensitive. If you hold the phone and cover that area (which is easy to do) signal strength will suffer (for example, if I cover the area with my hand, I go from 4 bars of 3G signal, to 5 bars of GSM only). This would normally be okay, but I find that this really causes problems and timeouts if you happen to be using a data connection (things will time out, the connection will be connected but appear dead, etc.) AND, the phone takes its sweet time to pick up a 3G signal again once you leave it alone. You can Google this to read up on the details. The bottom line is that I seriously considered returning the phone - until I looked up Makro's policy that they will not refund phones, they will send them to the manufacturer and leave it at their discretion. There IS hope that perhaps a firmware upgrade will alleviate the problem (especially since data connections become unusable where they should actually degrade gracefully), but I'm not holding my breath on that. I'm not sending a brand new phone to some clueless Nokia person that is going to take it apart, put it back together haphazardly (so it will never be the same again) and then tell me there is nothing wrong with it, all the while being without a phone...
Hmm. Thanks for the info. Will have to check MTN's policy before I pick mine up.
Oh and the iPhone 3G also had some problems with its 3G connection. Is that sorted out now?