Yes and no. Incarnum is more than a magic item system and less than a magic/psionic system. It's solidly in between.
Incarnum is the power source, essentia is the personal capacity to tap that power source and soul melds are the physical manifestation formed from that power source. Essentia use is similar to the force, in that a user of Incarnum taps into their own personal ability to channel it to gain special abilities and effects. Where the Jedi may have a Force Jump, an Incarnum user might be able to channel some of his essentia capacity into his jumping ability, temporarily. The Jedi then decides to use the Force to make him faster...so to does the Incarnum user speed himself up...in fact if he's a duskling, it's a racial ability.
The analogy breaks down with soul melds. A jedi uses a piece of equipment as his chosen weapon, the lightsaber. The Incarnum user binds a soulmeld to his hand chakra, such as the Blademeld prestige class, which is primarily a fighter who can summon a magic sword composed entirely of Incarnum.
Now here's one of the big differences from other systems and, IMHO, a critical difference both mechanically and conceptually: they never run out. Incarnum is not consumed nor is it truly transformed. This sounds minor at first, but actually has some signifcant differences. As an Incarnum user becomes more skilled at creating melds and using his essentia, he gains more options, allowing him to transform his abilities and soulmelds. Unlike traditional spells, soulmelds stay in place until disrupted; a character could summon armor made from Incarnum and then keep it until he choose to dismiss it. In an emergency, he could change the soulmeld to something that might be more appropriate or useful.
Example: An incarnum character wishes to emulate the character of Beet the Vandel Buster from the anime series of the same name. That character can summon one of five weapons (powered by the souls of some powerful warriors) from within himself, to do battle with monsters. During a battle, it becomes clear that his spear is useless against the skeleton he's battling...so he changes the soul-meld into a hammer and resumes the battle. He realizes, however, that he needs more power, so he channels his essentia using a feat to increase his battle prowess...however, to do so, he's going to have to stop using it to increase his speed. He does so, smashing the monster handily. He then switches his essentia to temporarily increase his hit points as more monsters arrive, and so on and so forth.
Incarnum is NOT a replacement for a full-blown magic system. It lacks quite a bit of functionality that the traditional D&D magic system has (which is fine, as long as everyone realizes that some kinds of resources aren't going to be available). It could be a replacement for a traditional magic item system, but that practically requires most characters multiclass into one of the Incarnum classes or races to reap any real benefit (although some of the prestige classes, like the blademeld, don't have such requirements).
In short, I agree that essentia use (on several levels) is similar in style to the use of the Force. But it also is radically different in other areas. Adding in the concept of soulmelds and some of the various abilities, I think that it's more of a superficial resemblance...I tend to think of the Psionics system as much closer to the Force than Incarnum.