There are several posts mentioning that ordering special meal on TATL is a good idea.
Could you, please, share you experience with special meals. What kind special meals did your order? What did you receive? Quality comparing to standard meal?
US Airways site is mentioning following types of special meal:
Kosher
Low sodium
Gluten free
Moslem
Low fat/low cholesterol
Asian vegetarian
Hindu
Low calorie
Non-lactose
Vegan
Diabetic
Baby
Lacto ovo
Bland
Childrens

Recently, Mr b1513 and I ordered a low fat/low cholesterol and a gluten free meal, respectively. We both got the same meal. It was baked haddock with rice and vegetables along with a salad like everyone else got. The meals were satisfactory but, on the return, we both ended up getting food off the menu. Let's face it, it's hard to get 'great' food in either of the categories from which we ordered. This was in Envoy.

Bobette

I've ordered the ovo-lacto vegetarian meal a number of times, in both economy and business. Generally the portion sizes have been comparable to normal meals, but I've been disappointed in the flavor.

My guess is that for the sake of simplicity and cost, the food service companies often have meals that satisfy a number of special meal requests, as the ovo-lacto meals typically seem to meet the requirements of vegan, bland, low-fat, and low-sodium too. The typical meal is often something like steamed or grilled vegetables and rice pilaf (with little or no oil or salt), small salad with low-fat dressing, roll, margarine, and a bit of fruit for dessert. A pre-arrival snack may be a plain, whole-grain roll with some tomato and cucumber on it. I'm sure these meals are wonderfully healthy for me, but they don't have much flavor and don't leave me feeling very full.

Fortunately these days, US seems to be including a meatless meal more often on their standard menu (Virgin Atlantic has been doing this for some time). They specifically mention vegetarian meals for Envoy on their website, though I'm not sure if they're regularly on the economy menu. These "regular" meals tend to be more rich and flavorful, being something like vegetarian lasagna or cheese-stuffed shells (don't get too excited -- they're still inflight meals). Of course, depending on this option has some risk, as US can make changes to their menu offering without notice, and they may simply run out of meatless "normal" meals before getting to you. Still, more recently I've been willing to "take the risk", while having some back-up snacks of my own in reserve.

The pasta option in coach is always vegetarian, but if you're in the last 5-10 rows it may not be an option for you. Just kindly ask the crew if it's possible to save one for you as you forgot to order the special meal you needed. The purser in the aft galley is best person to ask as they are the most informed as to the quantities of each meal catered and if there are possibly special meals that were ordered and the passenger is not on board. Politeness goes a long way!