Ignoring the suing crap Samsung's phones are in an odd place.
One one hand they do the job & they tend to have a decent spec so long as you avoid their cheapo stuff.
On the other there's a lot of little oddities with their 'Droid builds, that in turn causes app incompatibility & other crap that consumers shouldn't have to deal with. OFC if the app maker has a Samsung phone to test with they can cure it, but that's usually not the case. (the same applied to LG's old phones) It's a pretty low % since it's only 4.0+ specific stuff that has issues ATM, but it's still something that shouldn't happen.
From a dev standpoint (due to the above) a Samsung phone is a must.
Personally I find them meh, possibly because I've got used to all the bells & whistles HTC have in their Sense UI, maybe because the Samsung keyboard is fuck awful, I can't really tell. Nothing that can't be cured with a lot of apps, but you shouldn't have to.