This is not my first account (I had to get rid of the old one for personal reasons I won't go into) and I've seen a lot of changes over the years, both good and bad.
Bad things that really stand out to me are the removal of the First Name, Surname system. I actually LOVED that about SL when I first joined all those years ago and not being able to have that with this Avvie was actually such a bummer. I felt like it made it seem like your avvie actually was a real person rather than just a username, if that makes sense,
Secondly the orientation is awful. I swear when I first joined all those years back we had a tutorial of sorts with signs to read about how to change appearance, how to fly, how to do this and that where-as now all I remember is being thrown into it and expected to fend for myself (and don't even get me started on the starter mesh avatars, they are hideous and if you're knew with no idea how to take them off they are a big deterrant to new members imo).
Thirdly, although there are a lot of people I've found the people who actually do message me out of the blue are mostly people looking to cyber, otherwise people do keep to themselves, which I suppose I do too but I suffer from anxiety and I have always used SL as an outlet for social interaction without the pressure of being face-to-face but I do still find it hard to strike up conversation so I often find myself wandering around alone unless a friend is online and wants to explore with me.
As for the good, well it LOOKS better as a whole. I read a lot of bad things in this thread about mesh but I love the introduction of mesh. I sport an anime style avatar with the M3 head and Kemono body and it would have been impossible to look so cute before mesh but now I actually get to be how I want to be. I also found that the introduction of mesh has allowed me to really get into creating. I never got into texturing or prim making but I found mesh inspired me and now I'm actually doing constructive things which gets me excited to continue to learn and create. I feel like it's made me excited for the future in terms of creation and what could be achieved. They should have introduced mesh a long, long time ago IMO.