I did a ton of research before buying this phone, and I honestly feel it is overall the best out there for android(as of now)....Sure, its a smaller screen than the droid, but its a bit brighter, better viewing angles, and consumes less power..and it was the first android phone with the AMOLED screen, so that is kinda nice, only other one is the nexus one.
800mhz processor compared to droids 575-585mhz, and a better keyboard as well.
Obviously the droid has android 2.0/2.01, but sprint has announced moments will get 2.1 (just like the nexus one has) sometime in H12010, so no advantage to droid there either. Yea, only a 3.2mp camera, but honestly, most people have stand alone digital cameras for high end stuff anyways...for taking a picture in a bar with your friends, the moments camera is just fine.
The HTC HERO---only advantage it has is Sense UI, which is very nice, but being the very nature of openness of android, I dont consider anything software as an advantage, as hell, we might be able to root our moments and put Sense UI on them if someone gets crafty enough
In the end, I feel that at this time of whats available(excluding the nexus one which just came out), this phone has the best overall hardware package, and it will get even better once we are running 2.1 on it. (also battery life should improve with improved cpu scalling in 2.1) but remember, our phone sports a 800mhz processor compared to other android phones with 525-585, so our phones will always eat a little more juice when in use, but the lower power consumption of the screen should help offset that.
And all in all, ive been very happy with Samsung's quality in past devices, sure they have probably had a few bad products, but as a major electronics manufacturer, they have been on a steady climb for awhile now. While debatable, I think they have passed Sony in certain areas. (again, not really meaning phones, just electronics in general)
And while there is no fact in this next part, I feel samsung will be first to market with a 4G phone...sprint/clear, samsung, google are all part of the open handset alliance, and I honestly will not be terribly surprised to see a Moment 2 hit last Q 2010 with a 4-5 inch screen, 1ghz processor, 4G & 3G radios, and possible running VOIP factory from sprint.
I dont know about the rest of the states, but here in Texas, they have rolled out 4G big time, its in every major city, and most smaller ones too! (Hillsboro Texas has 4G...thats crazy..Hillsboro is like 20-30k people, that includes all the people driving through it on I35 as well!)
ok, off my soapbox now

but if you are on the fence...buy a Moment, you wont regret it
btw, technically the Nexus One is the best out as of now, however going to Tmobile was not an option for me, so my comments are based on the CDMA versions that were available to me.