OK, it's morning now.
Here are some basics.
The concept behind ADS-B is for aircraft to transmit their position data (derived from GPS or equivalent systems) out, so that the signal can be picked up by ground stations and relayed to ATC. This is supposed to reduce the need for radar installations but not replace it. This basic capability is called ADS-B OUT, and comes in two flavors
1090ES - by using the remaining free bits in a mode S transponder extended squitter data packet, an aircraft can satisfy the requirement. This is what the airlines like, and will be required for class A airspace usage (it is valid in all airspace). This is also the emerging standard in Europe as its what Eurocontrol is pursuing
978/UAT - this is a "new" datalink frequency, and it's what the FAA hopes will be used by all us piston folks who don't fly in class A airspace.
So, we have aircraft broadcasting their positions on two different frequencies, both of which the FAA can recieve. How does that benefit the aircraft? Basically it doesn't. It's supposed to reduce the cost of the ATC system be requiring less expensive radar infrastructure and reduce operations and maintenance costs.
That's the basics of ADS-B OUT. If you have 1090ES OUT, you can fly anywhere. If you have 978 OUT, you can fly anywhere except class A. If you don't have either one in 2020, you'll be locked out of some airspace the same way you are today without a transponder.
Now welcome to the weird wonderful world of ADS-B IN.
If you can make the aircraft listen on the ADS-B frequencies, then they can "hear" the surrounding traffic and display that information in cockpit. The FAA is also going to rebroadcast (ADS-R) the information they "hear" on one frequency out the other frequency, so if you have a 978 aircraft, you'll hear other 978 aircraft as well as the rebroadcast of nearby 1090ES aircraft. The delay is pretty small based on my observations, much less than the TIS-B information we may receive today. Note that currently we don't have an ADS-B replacement for TCAS, which is based on aircraft actively interrogating each other's Mode C transponders, so until that happens don't expect to replace your current transponder with an ADS-B box unless that also provides Mode C functions.
There's a lot of "room" in the 978 data link, and as a result the FAA will be implementing FIS-B (Flight Information Service-Broadcast) data which will contain weather, NOTAMS, TFRs, and other data that XM provides today. This information will be available whenever you're within receiving range of an ADS-B ground link, which will vary but be pretty good at 2000 AGL most places. Unlike satellite-based XM, the FIS-B signal may NOT be available on the ground unless you're close to a broadcast point.
So, depending on how you equip, you can have different services.
If you do the bare minimum - buy a Mode C/Mode S transponder with the 1090ES rebroadcast of a GPS position (either from an external certified receiver or from an internal receiver built into the unit), you'll comply with the rule and be able to fly in all airspace, and you may be able to show other traffic on a display. I believe, based on what I heard at AOPA this year, that Garmin has submitted a version of their current GTX330 unit for certification.
If you buy a UAT transceiver (I'm not aware of any UAT Transmit-only offerings) similar to the GDL-90, you'll comply with ADS-B out, be able to fly anywhere but class A, and also get the ability to display traffic and FIS-B.
If you want the whole package (fly anywhere, see all traffic in your vicinity even if the FAA gear is down, receive FIS-B stuff, and whatever comes down the pike) then you'll need 1090ES OUT and IN, and 978 IN at a minimum.
This stuff is still in it's infancy, and the FAA is encouraging manufacturers to get the technology inserted into their product cycles now. I believe they may even go so far as to award a contract to the vendors to cover the delta of the R&D costs so that the next models will include the technology. We'll have to see how quickly the avionics industry picks up on this stuff. What I expect to see eventually is a range of products up to and including the dual-band in/out unit.
Now, my personal experience. I've participated in several test efforts related to ADS-B. Recently I flew a test mission where we launched, waited for a UAT-equipped glider to be towed to altitude, and then flew converging and overtaking flight profiles "against" the glider. Gliders are HARD to see, but the UAT traffic data allowed us to pick them up much easier, so that we could easily maintain visual separation even as we flew directly over or under them (500 ft). Our test airplane was equipped on both bands and so we also were able to see the ADS-Rebroadcast of the glider's 978 signal on our 1090ES display. the position difference between the "real time" 978 display and the "rebroadcast" 1090ES display was pretty small, a lot smaller than I'd allow ANY blip to get to me, so I'll say that ADS-R is a big improvement over TIS-B.
Anyway, I've rambled enough except to say that the 10,000 price tag is for an early-model UAT transceiver, not a portable 978 MHz receiver. Those are in the 1,000 range.
