I'll throw my 2 cents into the mix. I just got my Z2 a couple of weeks ago. I really like it. I am moving from a D2+. The sound is great. It was easy to get google play on the Z2, and the apps I have tried work well. (pandora, espn radio, calengoo, word hero, dogcatcher, and a couple others). I am very pleased with the battery. It is of course not as good as the D2+, but I knew that going in. It is a little better than expected. The first day I used it over twelve hours playing some music, but mainly pandora, dog catcher, and espn radio. I left wifi on the entire time. It still had over 20% charge left. I will have to charge it at night, but I can live with that. I had been using my HTC Vivid phone for pandora and espn radio. The Vivid would die after just a few hours. Long before my workday was done it needed a charge. So it went to the truck to charge, and I was without my phone.
It does what I want, it gives me a great sounding media player with the bonus abilities of android and wifi. I am happy with it, and do not regret going with the Z2. I was pretty nervous, and afraid I would regret it. I ordered it from Amazon, and they said as long as it was ordered from and fufilled through them I had thirty days to return it. So I paid a little extra to get it from them, but it gave me peace of mind to know I was not stuck with it.
I have a couple minor things I wish were better. I do wish it had a better interface with music. Maybe I am just not used to it. The D2+ was pretty good once you got used to it. I can do without playlists as I very seldom used it to begin with. I just use the folder vies and make a folder for a playlist. Not elegant, but it works. I also would prefer the charger plug to be on the other end of the row of plugs. It is right next to where the flap attaches and is a little irritating. Very minor, and maybe it would bother me more elsewhere.
I needed a player to record fm radio, so I never really looked at other android players.