Note: very minor spoilers follow.
It's a neat, weird, amazing, twisted movie. I mean that in a good way. The title character is an absolute cypher, and has to be in order to make the movie work. The role really called for a guy like the young Dan Aykroyd - stiff, hard to read, but basically really likeable. This guy wasn't quite like Dan Aykroyd, but the way he played the role wasn't all that different.
This movie is chock-full of likeable weird people with lousy social skills. The only person that's particularly conventionally attractive is Gus, Lars's brother, and Gus is kind of an asshole for a lot of the movie. There's either a moral there, or the screenwriter is awkwardly likeable and wants revenge on the conventionally attractive people in his/her past.
The movie starts out as a mini-biography of Lars' awkwardness among people who like him but don't quite know what to make of him. It then moves on to him receiving the RealDoll he ordered. This would be kind of a surprise if you hadn't already read a brief synopsis of the movie somewhere. As is, it just seems -- well, sudden and random, since RealDolls had been mentioned only by the sleazy cube-mate at the office that spends his time surfing for porn.
Lars introduces "Bianca", the new RealDoll, as a woman of Brazilian/Danish ancestry who uses a wheelchair and whom he met on the internet. He moves her into the guest room in the house (remember, he lives in the garage), brings her to dinner, and generally treats her like, y'know, a person. That's the actual plot of this movie, in case you hadn't read the summary before. It's a small town humoring Lars to various degrees as he brings his RealDoll to go socialize, often among people and in places where he'd been too awkward to even show up before.
The RealDoll in the wheelchair is exactly the right kind of creepy for the role. Good purchasing on somebody's part.
For reasons I won't get into here, the movie slowly turns from gentle, bizarre comedy to weird, twisted psychodrama, with Lars and Bianca as twin centerpieces. The acting is fantastic, far better than I had given it credit for early on, especially on Lars' part.
This movie walks the line of certain art flicks that try hard to keep a central character weird, mysterious and hard to understand but allow us to really like him anyway. This movie manages not only that, but puts him through a variety of hard situations where he's under a lot of strain and we still pretty much come through liking him.
That's a hard line to walk, and they do a fine job of it.
Overall, I'd definitely recommend the movie to anybody who reads the two-line description and still thinks, "yeah, I think I'd like to see that."
A random aside: they don't mention the RealDoll parody site which has been around almost as long as RealDoll in the movie, but they should. Or at least, somebody really should.