I don't think they overdid the evolutions of previous Pokemon, because every generation has followed a pattern:
1st - all new (duh)
2nd - few new, lots of evos/pre evos
3rd - all new, very little pre evos (Azurill)
4th - few new, lots of evos/pre evos.
And as for my opinion on each:
Budew - cool, not the best though.
Roserade - AWESOME. My favorite grass Pokemon, making me like Roelia better too.
Ambipom - Kind of cool, but should look cuter, not tougher.
Mismagius - Same as ambipom, could have been designed better.
Honchkrow - cool, but could be better.
Chingling - awesome, makes me like Chimecho even better.
Bonsly - cool
Mime Jr. - I've grown on it, but didn't like it at first.
Happiny - I also like this one from the get go.
Munchlax - awesome, and cute
Mantyke - liked this one from the start.
Weavile - cool, just needs a better shiny form
Lickilicky - cool idea, just needs a better design. also forgetfull.
Rhyperior - cool, esp. shiny
Tangrowth - very forgetfull.
Electivire - cool, needs better shiny.
Magmortar - VERY ugly, shiny and normal.
Togekiss - AWESOME
Yanmega - cool, but forgetfull and too tough looking compared to cute Yanma.
Leafeon/Glaceon - very good eeveelutions.
Gliscor - see Yanmega
Mamoswine - GREAT addition to the Swinub family.
Porygon Z - cool design, but I think that all of the Porygon family should be able to change depending on its held item.
Gallade - coolest, made Ralts family even better than before.
Probopass - very forgetfull
Dusknor - cool
Frosslass - great addition to Snorunt family