According to Bosch there is no confusion:

Driver's: Bosch Icon 424A 24"
Passenger's: Bosch Icon 422B 22"
Rear: Bosch Hindsight 40818 18" - which unfortunately are no longer being made and they do not have a replacement!

If you feel that the Bosch Icon 422B 22" passenger wiper is too long (though I've tested it and it isn't too long and fits perfectly...read my note about it at the bottom of this post though), get the Bosch Icon 421B 21" wiper. A and B refer to the pressure or 'spring tension' of the wiper and not so much fitment (driver side versus passenger side). The "A" variant has less curvature and spring tension and is used on the driver side since the windshield is essentially flat. The ""B" variant has more curvature and spring tension to it and that is why it's used typically on the passenger side where the windshield is more curved and not as flat.

Since Bosch no longer make a wiper for the rear you can try the Bosch Icon 418A or 418B, though they do not recommend it for reasons they cannot explain very well, people on the site have reported the 418B to work well. I don't know about the 418A.

Another option if you want the newer style wipers blades (like the Bosch Icons) then you can get the Valeo 900 Series (Ultimate's) (which I believe is what all new BMW's come with now) in 24" and 22" size:
Driver Side: 900-24-1B
Passenger Side: 900-22-1B
Rear: None specified

Valeo also introduced a "Gen 2" wiper, but according to their technical support line, the 900 Series are still much better. One interesting thing to note is that they do spec a Gen 2 wiper for the rear window (model U-18), however their tech support says the 600 Series Premium wiper (model 600-18, which apparently requires a "T2" adapter) is a better wiper than the Gen 2 model, and their best rear wiper.

(Of note, the OE BMW wipers were made by SWF, which is Valeo. I believe they were the 800 Series).

Update: Apparently BMW now specs for the E92 and E93 a new wiper blade which is the "Neoform Beam Style" wiper blades. I believe these are made by Trico. It's worth noting that they retail for DOUBLE the cost of Bosch Icon's or Valeo 900 (Ultimate's). The BMW E53 X5 relevant part numbers for these blades (in case anyone wants to try them out) are:
Driver Side: T16-240
Passenger Side: T16-220
Rear: T16-180

Here are the relevant links:

Bosch
Vehicle Part Finder

Valeo (1-888-718-2536)
Valeo Wiper Systems - Valeo Wipers Online Catalog

Trico
Online Catalog

As far as replacement intervals go, BMW used to specify replacement twice a year (before and after the winter season) and with the free maintenance they did it twice a year no problem. Now they have increased that interval to once a year for the free replacements.

In regard to fitment:

- The Bosch ICON 424A fits perfectly and does require the removal of the "U" shaped guide. That little plastic part can simply be pulled off (for reusing at another time) and need not be "broken" off. Their fitment guide states this as well ("Plastic clip must be removed from Driver Side Wiper Arm before installing ICON Blade"). Also, it seems that a longer wiper (like 25") would even fit, however the next size up is a 26" wiper. It would be interesting to see if a 26" wiper cut down to 25" would be effective.

- The Bosch ICON 422B seems to not have enough tension at the last outer inch in order to make complete contact with the windshield.

- This is just speculation, but maybe the reason Bosch does not spec an Icon blade for the rear (such as the 418A or 418B) is that the original wiper arm has a "U" shaped clip that cannot be simply removed, but must actually be broken off (unlike the case with the "U" shaped clip on the driver's side wiper arm) since it is riveted to the wiper arm itself.

- The Trico T16-180 wiper for the rear fits well and fortunately does not require removal of the "U" shaped clip. Since it is a much lower profile wiper than the stock wiper it actually contacts the glass and passes under the clip without making any contact with it.