Indeed the limousine bus is convenient in that it will take you from the airport to your hotel in Tokyo, still it's very subjuct to possible traffic jams.
The Limousine Bus Company offers a page where current durations to each destination are listed. Unfortunately, the service is only in Japanese, so I'd translate the names of the destinations etc. You can refer to the site at the same time of day and week as you plan to travel before you come to Japan to see how long your trip will likely take.
Current limousine bus durations
成田空港路線（ 17:03 現在） / Narita Airport Route ( As of 17:03 hrs on 3 Sep 2008)
| 出発地 → 目的地 Origin -> Destination | 所要時間 Duration (minutes) |
| 成田空港 → 羽田空港 Narita Airport (NRT) -> Haneda Airport | 55分 55 minutes |
| 成田空港 → 新宿駅西口 NRT -> Shinjuku Station West Exit | 75分 75 minutes |
| 成田空港 → 東京ｼﾃｨｴｱﾀｰﾐﾅﾙ NRT -> Tokyo City Air Terminal (TCAT) | 54分 54 minutes |
| 成田空港 → 池袋/ｻﾝｼｬｲﾝﾌﾟﾘﾝｽ NRT -> Ikebukuro / Sunshine Prince | 75分 75 minutes |
| 成田空港 → 横浜ｼﾃｨｴｱﾀｰﾐﾅﾙ NRT -> Yokohama City Air Terminal (YCAT) | 109分 109 minutes |
| 成田空港 → 赤坂（ANAﾎﾃﾙ） NRT -> Akasaka (ANA Intercontinental) | 67分 67 minutes |
| 成田空港 → 渋谷（ｾﾙﾘｱﾝ東急） NRT -> Shibuya (Cerulean Tokyu) | 72分 72 minutes |
| 成田空港 → 品川（ﾎﾃﾙﾊﾟｼﾌｨｯｸ） NRT -> Shinagawa (Hotel Pacific) | 68分 68 minutes |
上記の数値は実績値であり、到着時間をお約束するものではありません。
これからの道路状況により多少の早着・延着の可能性もございますので、目安としてご利用ください。
The figures above are the track records, and the arrival times can't be guaranteed.
The coach may arrive slightly earlier or later than them depending on traffic from now onwards. Please utilize this chart only to get a rough idea on the duration.
----- ----- ----- ----- -----
Of course you can ask the ticket sales clerk at Narita Airport how many minutes it will take you to get to your destination when you're about to purchase a ticket. If it sounds too long, you might just as well switch to the train.
----- ----- ----- ----- -----
As of 18 Sep, 2008, there is a page stating the current durations of the limousine bus service in English...Sorry for the fact that I've missed it.
Limousine bus current durations in English
.
