Lots of new students of the Japanese language often rely too heavily on Romaji (also know as the Roman alphabet) to get by while they are studying or figuring out Japanese. This is primarily because whenever we first start learning Japanese, you want to jump right in and learn to speak the language. Just studying Hiragana or Katakana can take a while, and after you really can't even comprehend much (you can read, yes, but fully grasp...no).
Am I simply bothering you like your Japanese teacher? What is the real downside to using the Roman alphabet?:
You Are Presently Used to Romaji
You are currently familiar with saying things a certain way when you read Romaji letters. Japanese characters, alternatively are fresh to you and you will not need to be worried about this. The mere point that you are not familiar with pronouncing Japanese characters in a particular way is actually very beneficial for you. You can essentially start from scratch and benefit from an infinitely more natural and quicker way to become smooth with your pronunciation.
You Will Not See Much Romaji in Japan
Okay, you school textbooks may well use Romaji (and if they persist on using it for longer than instructing you on Hiragana, I would honestly think about finding some new books), but You will not likely find much Romaji getting used in Japan. Not even in modern metropolitan areas like Tokyo or Osaka. You'll likely just see names of department stores written in Romaji and maybe a handful of English words. Japanese people just do not use Romaji.
Today's Shortcut is Tomorrow's Liability
If even a tiny part of you would like to really master Japanese and try to get fluent, you will sooner or later have to forget about the Romaji and learn some Japanese symbols. It's a lot easier to do this right from the start than to wait a few month or years.
Alright, so Romaji seriously is not the easiest way to go. What should you do when you're just starting out? It certainly is dependent upon what type of Japanese student you are. From my perspective, there's two kinds of Japanese students:
The Committed Student
Maybe you are studying Japanese in college. Maybe you're going to live in Tokyo for a couple of months or a year. Maybe you are a business person that has several Japanese clients. Or maybe you simply have a lot of Japanese friends and you are tired with them talking about you behind your back.
If this represents you, the very best thing you can do is to sit down and master Hiragana and Katakana. These are definitely not difficult to master and by taking it a little bit at a time and going at your own speed, you can most likely learn them in a few weeks by using some flash-cards. As soon as you get good at the Kana, you should have a quality foundation to build on and you may begin learning vocab, sentence structure, and the rest of the things on the correct foot.
The Hobbyist
Maybe you are going to Japan for a fast vacation. Maybe you truly like anime and want to find out more on the culture. Maybe you simply have some spare time and want to learn one or two languages for the fun of it.
If you are like this, my suggestion is to begin with some simple conversational Japanese instruction. These can be less difficult than trying to read and write Japanese at the same time, plus they are much more useful if you're traveling to Japan as a visitor and all you really want to do is ask where the taxi is. Once you've got some straightforward conversational Japanese down, it could be that you might choose to take it further and really learn the language diligently. Moving ahead you'll be in the ideal position to take the path listed above and learn all the Japanese characters (including all those pesky Kanji).
So I hope you can comprehend now why relying on Romaji really isn't to your advantage. It doesn't matter what your eventual goals are with learning Japanese, you will end up significantly better off if you spend the trouble by leaving the crutch behind and either master Hiragana and Katakana or practice some conversational Japanese.
