Well I came from a 4yr stint with my original Galaxy S (I9000) so it is a HUGE improvement lol I was going to upgrade to the S4 but when it came out I hated the design so thought the G2, but I couldn't do without an SD card and removable battery..then thought the S5/M8 but S5 design is **** & boring let's face it and the M8 is just a phone for sheep as everyone and their dog will get it because simply, it looks fantastic (like Beats headphones, but unlike Beats it actually IS real quality lol). Also, when I went into Carphone Warehouse, the advisor there told me the best phone they had was the M8 or alternatively the G3 second. The M8 is robust and solidly built and had never been brought back for repair in that particular shop. He said the G3 was just as good but that most people went on brand name so didn't trust or know what it had to offer; himself included until an LG rep came and showed them. He told me to stay away from all Samsung phones (S5/Note 3) as they are the top returns for repair with such things as the battery expanding so it doesn't fit anymore.
Yes I miss the opportunities for custom ROMs but I'm sure this will happen soon as it does with every phone - is there actually any phone that cannot absolutely be hacked in some way at some stage? The other thing is that Samsung officially stopped supporting the I9000 2yrs after they released it so I think ICS was the last official ROM and to get GB you had to install custom. Tbh I remember reading and hearing from people that LG pretty much do the same thing but thesedays that doesn't matter to me as I would never stay stuck on stock if there are custom ROMs available, and I'm positive that most phones will have active development communities for years past their sell by date.
I am extremely happy with my G3 and not sure if I would go back to Samsung again in the future when there are so many worthy and equal/superior contenders out now.