First, a disclaimer: I don’t always use a siddur [prayerbook]. I normally daven at shuls which are nusach sfard, and I am an Ashkenazi boy. Nusach Sfard siddurim are a distraction, and I often leave my own pocket siddur in the wrong pockets.
Nonetheless, I believe that one should use a siddur, and particularly for the amidah. Aside from the halachic reasons favoring siddur-based prayer (see, for example, the Rama in Shulchan Aruch Orach Chaim 99:3 and 100:1, and Mishneh Berurah 53:87), there are many other reasons why one should use a siddur. Among them:
A siddur guarantees that you don’t miss words or get lost in the middle of the Shir Shel Yom for Wednesday;
A siddur held before your chest can protect you from stray bullets, and earn you a wonderful story you can tell for decades to come, assuming your siddur has enough pages to do the job;
A siddur can assure that you won’t be interrupted during davening by a well-meaning friend who thinks you want to know the latest football score. Staring into a siddur clarifies for the world that, yes, you are davening;
A siddur of sufficient weight anchors you, keeping you from wandering too far across the shul and away from your makom.
A siddur – assuming you look into its pages and do not only hold it closed upon your heart, its shieldworthiness notwithstanding – can focus your eyes so that they don’t wander around the room and make contact with mine twice during your amidah, giving the false impression that you are daydreaming rather than davening.
And a siddur is an accessory, even a fashion statement, a way for you to affiliate with those who are like-minded. Artscroll, Koren, RCA, Birnbaum, Tikkun Meir, Shiloh, etc, all of these send important messages about your identity. Note that this is especially important in your shidduch years.
The classic, timeless, siddur: It’s the way to go.