Some general question about thredds/opendap

I'm evaluating the usage of thredds for an EU project 
http://www.ecmwf.int/research/EU_projects/GEMS/

I installed the 2.0 version and was able to browse some pages and see 
some data, but I still have some more general questions:

What are the main advantages of thredds against opendap?

I see a lot of XML files and the last s in thredds is for services: What 
is the relation between thredds and web-services 
(http://www.w3.org/2002/ws/) or REST 
(http://www.xfront.com/REST-Web-Services.html).

Does thredds include a opendap server (didn't manage to get that 
working), or is thredds just able to distribute data via an external 
opendap server. If yes: Is the thredds opendap server able to serve as 
much data as the generic opendap servers, i.e. grib,hdf4,hdf5?

What is the status of thredds (3.0?), the aggregation server and the 
query language to search the aggr. server?

Best regards,

Heiko

--
Dr. Heiko Klein                              Tel. + 47 22 96 33 44
Air pollution Section/Research Department    Fax. + 47 22 69 63 55
Norwegian Meteorological Institute           http://www.met.no
P.O. Box 43 Blindern  0313 Oslo NORWAY       http://www.emep.int