I wasn't the biggest fan of the V5 or V6. I don't know why, they just don't appeal to me. I don't regret them so much as wish I had saved my money for something else.
Hmm, well I don't really like the P1, even though I got it for really cheap. I liked the Angelgotchi because of it's cute characters and the tapping feature (and shell design), but for some reason the P1 wasn't fun and I didn't really like the characters either. Plus, the shell design isn't really that special.
Otherwise, I don't really regret buying anything. I think TamaTalk has taught me a lesson: Read before buying, folks!
I don't think I have enough tamagotchi's to say I regret buying any as I only have 2 but I am worried that maybe I'll regret getting back into it for the cost reasons... lol
I dislike my v5 I took the battery out after a week. I tried giving it several chances, but each time I gave up on it. I thought it was harder to get attached to because there were 3 tamas and I liked spoiling one. I just don't like it. Sorry guys!
I don't think I've fully regretted buying one yet. I do sometimes regret which ones I get first and for not waiting longer to get some of them so that I pay less.
I think the one I was mostly disappointed in was the TamaGo. I got it when I started getting back into TMGCs with what little money I had at the time, wish I'd just waited and put the money towards a different version on eBay or something because I rarely play with it if I'm honest so for it just to sit in my collection it could have waited.
Last summer, when i just started getting back to Vpets. I went on Amazon and for $10 I was able to get either a JD fake, either a Gotchi gear watch... guess what I choose xP I really regretted not getting the watch :/