I thought I already posted my thoughts about TMP, but looks like I didn't. Better get it in before we switch to Voyager.
TMP was actually my first experience with Star Trek. I was about seven or eight yeas old and very into Star Wars, so getting into Star Trek felt like a natural progression.
The one thing that really stands out to me about viewing it as a child is that it was a rather frightening, eerie experience (despite being rated "G"). The Klingon ships slowly being disintegrated by a big cloud and not really understanding what was going on, seeing the transporter accident before I knew what a transporter actually was and wondering why those people got killed, the wormhole effect where time seemed to slow done and get all shaky, what happened to the bald chick after she disappeared and came back with a car cigarette lighter in her throat. And V'ger itself, a giant cloud that seemed to destroy everything in its path, heading toward Earth -- and the Enterprise flew right into it, and I couldn't tell where the cloud ended and whatever was inside of it began.
To my eight-year old mind, TMP was mysterious and puzzling and frightening, and it left me wanting more.
So I've always had a soft spot for it.