Coming from a collie person, who has grown up with a collie breeder and been around more collies in her day than most people will ever imagine, I have quite a bit of input here.
First of all, collies are wonderful. I love them with everything in me. I don't think I will ever NOT have a collie. I need them like I need air. That said, they are not by any means the superdog that everyone seems to think.
They have a lot of health issues such as the above mentioned ivermectin sensitivity. The are becoming more and more known for having demodex mites, and I have seen some mild cases and I have seen some SEVERE cases. I don't have my pictures of Tess, my little sweet demodex pup online anymore, but I can describe it to you pretty well. Tess was bought as a show pup and to be introduced to my stepmoms breeding lines. Sweetest little thing, very lovey, very cuddly. She started finding spots on her body that had almost thinning hair. Took her, did a skin scrape. Demodex. The mites tore that dog apart. She was COMPLETELY hairless. Her skin was raw and constantly needed to be cared for. The problem with collies being ivermectin sensitive is not heartworm meds, you see, because there are other meds out there for heartworm, but rather that demodex is most easily treated with ivermectin. Most dogs with problems are able to clear up rather easily. But because some collies can't have ivermectin, and ivermectin helps demodex... well, you can see the problem. Tess did manage to kick it and get better after several years of battling it. She was a strong willed dog. I miss her a lot. She died a few years ago.
Also related to health, is that sensitive collie tummy. Faith has overcome most of her issues by me constantly (every three months or so) changing her food to get her acclimated to variety. I am a FIRM believer that variety helps eliminate a lot of sensitivity problems for a lot of dogs. I've seen it work. But, she has had to overcome a lot. I have seen many collies that needed to be on very basic foods. Need that more sensitive diet. I won't even begin about collie eyes. There is so much to say about them and I am a bit sleepy, lol.
Okay, onto temperment. I, with a passion, LOVE LOVE LOVE the collie temperment. That is the main turn on for this breed for me. They are very... almost mother like. So sweet, so gentle. It's funny that you mentioned that you had a rat that rode your shelties back, because James, my big ole fat rattie rides Faithey all the time. She licks, cleans, mothers, and just adores him. She is like that with everything. I rescued a baby bird once after I watched a cat eat it's momma. Faith wanted that bird so bad. She would watch it all day long. When he came out for feedings, she would lick at him and try and clean and mother him.
Faithey is a one person dog (unless you have food). She is a total mommas girl. She loves her daddy, but if she is not able to get to mommy then she cries. For example, I work at a pet store that they come into all the time. They will visit me and I'll be with them and then get called to help a customer. As I walk away, Faith will literally sob. It breaks a mommas heart. She cuddles me. When she wants too. She's not overly cuddly, but she will want to be by you. She used to follow me all over the house. Since we moved into a smaller house, she hasn't needed too. She can always find me by moving a few feet, lol.
Okay, health and temperment aside, someone has mentioned something about collies being intelligent. I beg to differ. I mean, look at the head shape. There is no room for a big brain in there. They are absolutely intuitive, but don't mistake that for intelligence, lol. Okay, I have had a few "smart" collies before. My Piper was insanely intelligent. Tess was as well. But, mostly, my collies have all had this "ditzy blonde" type of thing going on. Or at least all my girls. Keeping in mind, my stepmom bred them, so we had mostly girls. Faith is by far the most unintelligent collie I have ever known. She has no brains, lol. She walks into walls, can't figure out how to step over a pillow and a coat on the ground (instead, she jumps all the way on the bed after crying for 20 minutes), can't understand how to jump over a small fence after having done it minutes before. She just isn't smart. She's trainable. It doesn't take long for her to catch on to a new command or trick. But, she lacks problem solving skills to a severe degree.
I'll try and name some of the ones I have had. I don't breed, never will. I rescue, but I did grow up with a breeder, so I have had a lot.
Star, Abbie, Domino, Piper, Tess, Leah, Destiny, Haley, Ruler, Luke, Benton, Gabby, oh I can't remember them all. That's another reason I don't like breeding, I can't even remember all the dogs.
Now, I apoligize if what I just said was worded weird as I am tired, sick, and on meds, lol. But, I think I managed to get my point across. Onto the pics.
Faith at 11 weeks
My girl grown up.