Although still possessed of that famous impatience...
This is well indicated by Maul's appearance on the balcony, and while Sidious muses upon the history of the Sith, Maul shifts impatiently. Eventually he speaks, saying he will find these Jedi quickly, and contrary to what we hear on-screen, his voice is described as rough. After speaking, he waits impatiently for a response from his Master. His manner is that of keen anticipation, for he looks forward very much to this encounter with his hated enemy. Later in the book, when he sends the probe droids to find the Jedi on Tatooine, he smiles faintly at the thought of their future battle, for battle it will be. Soon, he thinks, soon. Later still, when Sidious speaks to Maul and the Neimoidians on Naboo, and he learns that the queen's starship has been found, he counsels Maul to be patient, and to 'let them make the first move'.
Mauls presence scares the Neimoidians almost out of their wits.
In fact, the effect of Maul's presence on others is truly terrifying. When Sidious first presents his Apprentice to the Neimoidians, they are stunned into silence and Nute Gunray averts his eyes from the monster in front of him, Maul. Maul is described as having gleaming yellow eyes, which fix on the Neimoidians, and break past their defences, stripping them bare and dismissing them. (Note that Maul is described here in full colour, with yellow eyes and red and black tattoos, yet the hologram is shades of blue and black).
When Maul finally confronts the two Jedi in the hangar, at Theed, his face is described as 'feral', a terrifying mask, and his yellow eyes bright with anticipation and rage, as he holds his long-handled lightsabre before him. Maul ignites the sabre, presents it to the Jedi, and smiles as he swings the weapon before him and beckons them to the fight. It is quite apparent that Maul has looked forward to this meeting for some time...
A mature warrior? Yes, but he howls a challenge to battle. Perhaps this is a primitive reflex of his species, the Zabrak. When he attacks Qui Gon for the first time, in the desert, his howl is 'a hunter's challenge to his prey', and his face is alight with a killing frenzy that promised no quarter.
When he confronts the Jedi in the final battle, there are interesting comparisons with Jedi techniques, for Qui Gon Jinn, the great swordsman, recognised that Maul was totally focused on the task in hand. A Jedi's focus, mindful of the present, locked in on what was needed in the here and now. In fact, although Qui Gon saw madness in his eyes, Maul was a living example to him, of how best to bear the will of the Force. As MaulMaus has pointed out, this is probably the most generous 'official' comment anywhere in canon, about Maul.
As far as enjoying the battle goes, remember that in The Journal, the author (Maul) says he does not speak while fighting, for he prefers to concentrate on the joy of killing. The novel then describes his strange face shining with the heat of battle and his own peculiar joy. And why not? Maul is an athlete, and the effective use of one's body must be distinctly pleasurable, putting into fullest effect all those moves he has learned and practiced over the years, in preparation for this day. Of course, it is entirely possible that this joy is almost sexual in it's intensity, something fans have speculated upon quite avidly.