A lot of things you might hear about the Rahxephon movie is how most of it is just copied and pasted from the series, how it's rushed and makes very little sense. This is true. BUT you need to take into consideration two things: this movie was not a theatrical release, but a made-for-TV special. Secondly, NHK demanded this movie from Bones with a ludicrous deadline that they barely completed as it is. So, with that in mind...
I think, as a stand-alone "movie", it sucks. Which is no great surprise to anybody. I do, however, think it's a great supplement to the series. It's really best if you watch it DIRECTLY after seeing the last episode with no break in between. I find it's like End of Eva for me, in that it should theoretically be very confusing, but actually clears up a lot I didn't understand about the series' ending.
The movie is technically an AU or re-telling, but even so it helps clarify the series' version rather than make a completely new and bizarre one. So, as long as you're talking about it as part of the series, I really don't think it's so bad.
