The problem here is these changes were what smn needed, not what people wanted: The wanted part being the catch here.
The class will now have:
A method to AoE apply all their dots simultaneously
Have more interaction/abilities to existing Egi
Burst... a lot more burst.. gods we needed this.
Bahamut... we get bahamut. What says summoner more than bahamut? I don't understand... we didn't get get that in XI
The trance system could be the first step in what might be future trance abilities from other primals. We may end up seeind Trance garuda/Ifrit/Etc. It could be a method for them to help us fill in a void where we need certain types of DPS.
As for the egi appearance, looking through the history on just these forums.. not to mention reddit.... You can find god knows how many pots on Egi appearance alone. This is the first step towards addressing this. I remember a lot of people wanting carbuncle back.. well here you go!
As for the nitty gritty mechanics, we don't know. Spell speed was mentioned as being reworked for us a while back as Dement said. How? They didn't say. Until we get our hands on it, we don't know. But IMO this is what the job needed, esp in raid.