New Syntax
Some people wont agree, but since I've been using Twig the "for ... else" feels right. It might not be a lot, but it keeps my templates that little bit cleaner.
{% for row in articles %}
Display articles ...
{% else %}
No articles.
{% endfor %}
Automatic Escaping
You can have the template engine automatically escape any output. This is great as you no longer have to repeat htmlspecialchars ... everywhere. Twig does this nicely.
{% autoescape on %}
Everything will be automatically escaped in this block
{% endautoescape %}
Template Inheritance
Another feature I like is the ability to extend base templates. Here's a basic example
base.html template
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang="en">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
{% block head %}
<link rel="stylesheet" href="style.css" />
<title>{% block title %}{% endblock %} - My Webpage</title>
{% endblock %}
</head>
<body>
<div id="content">{% block content %}{% endblock %}</div>
<div id="footer">
{% block footer %}
© Copyright 2009 by <a href="http://domain.invalid/">you</a>.
{% endblock %}
</div>
</body>
child.html template
{% extends "base.html" %}
{% block title %}Index{% endblock %}
{% block head %}
{% parent %}
<style type="text/css">
.important { color: #336699; }
</style>
{% endblock %}
{% block content %}
<h1>Index</h1>
<p class="important">
Welcome on my awesome homepage.
</p>
{% endblock %}
A child template can override blocks for page specific styles, content, etc ... You can also notice the use of {% parent %} which grabs the parents content so you don't lose it all while overriding.
I recommend you give Twig a go. Extremely useful.