I actually like the new update, they're squashing bugs while adding small features to the game. Example, 1.3 adds the option to farm cocoa beans using a new type of plant. This has been a requested feature since cocoa beans were added in Beta 1.2, if memory serves me correctly. Many other small, but effective things have been changed, like stackable buckets and signs.
The game has taken a different path, this does not mean they're trying to "pull in money" or something. Modding support has been a suggested feature for a long time, and takes time to implement. Mojang cannot create the perfect game for everyone, that's why mods are here to change the game to your likings. An official modding API will allow us to easily install the mods we want. You may be experiencing FPS decrease because of how they made singleplayer like a shell over a multiplayer server. 1.3 isn't that bad and should get improved with time, and Mojang can only work so fast as a small company.
Poll