You haven't missed much. You've missed Rubbish, Rubbish, and maybe the iD and iD L are not rubbish but not nearly as good as mid-connections. Mid-connections (V3 to V5.5) are awesome, but anything before is boring and anything after is too needy, in my opinion.
But they are only rubbish for me. If you have a lot of time and you're an absolute Tama freak and you don't have school or a job or anything, then the Music Star or Tama-Go would be perfect. But if you're an average teen, with homework and a Saturday job and after school clubs and that sorta stuff, then mid-connections would suit you best.
It's different for everyone. Maybe run a Music Star or Tama-Go during the holidays, and switch back to a V4 or something when school starts again. I prefer to just run my V5 full time, but each to his own.
Also, I'd use these words to describe the positive features of a Tama-Go:
More pet-like
More repetitive (get used to the same old characters, no switching families like the V5)
Simple (no "oh wait I need the Cheerful family with 80% bonding and one Intelligent chararcter and I got to check a growth chart")
It's anything BUT cool and interesting, really.
Design your own house - there are about six different styles you can buy. Some are quite rare.
Park - either meet another character and get happy or don't meet another character and get sad. It gets your Friendship Level up (Friendship Level gets higher by playing games or going to the Park. It influences the character you get)
Figures - get two extra games and a shop. About 1/3 of the games are almost exact copies of games from V3 to V5. Some of them are quite fun and challenging.
It's the truth, I own five working Tama-Gos and about ten figures. And they were all a waste of money.
I'd say, overall, the Tama-Go isn't reviewed as good by most people round here, and the Music Star is slightly more popular. If you're the type who was around when the P1s were in stores, then I'd stick with vintages and earlier connections.