bear in mind that Spotify is still a very new site and they are uploading thousands of new tracks daily ...
they only recently added the function where you can download a track for a few pence to iphone etc, so many of the artists who have opted out of having their music played on spotify, may change their minds in time to come
as for playing the album seamlessly, I don't fully understand the question? .... If you have spotify premium (a tenner a month), there are no adverts and the tracks/playlists should play seamlessly... you also get 320kpb instead of 196 (think that is the figures?) ... if it is not, perhaps clean your computer/cache?
there also used to be an option where you upgrade the free version for a day pass if you are on spotify free ... costs a pound or so, and you get 24hrs of uninterupted music (without adverts at the 196kpb bandwidth), and was marketed for when you have a party etc .... I never used this but am sure it is still available
I think that spotify will do extremely well ... they only function in a few countries at the moment, and are expanding daily ... when the hit the USA, I think there will be zillions of new tracks added
I have been using spotify for several months now, and think its the best thing since sliced bread ... I have heard so much new music/artists and have spent a lot of money buying new cd's
For those who cannot get spotify yet, there is another site called grooveshark
http://listen.grooveshark.com/
similar to spotify .... it's free (I have not really used this site extensively, but have had a quick look and it seems ok)
there is also a free program that runs in conjuction with spotify .... it allows you to find music similar to a specific artist/band and when you click on a result, it automatically plays the track in spotify .... works ok, ... program is called spotibot and here is the link:
http://spotibot.com/playlist/