i'll get Website Error if i'm trying to search something.
Put the site in dev mode so you at least get some useful error messaging - http://doc.silverstripe.com/doku.php?id=debugging. Just add Director::set_environment_type("dev"); in your _config file which you will see the actual error output which will give you a clue to what is wrong
also the implemantion of jquery as additional framework is nearly impossible
Are you talking about the front end or the backend? While it is not ideal at the moment it should not nearly be 'impossible'. We are undertaking a large about of jquery work over the next 3 months so the JS inside SS will be cleaned right up for 2.4
each module works for its own, but many of them together fail
Because of the many, many combinations that could occur we cannot test all of them together for every instance. We do test the latest trunk builds together via integration testing but if you do see a bug please report it so we can do something about it :)
i hope the developers will fix a lot of bugs in the next weeks
The core developers are constantly working on the modules and cms for our projects but if you find any issues please raise them on open.silverstripe.org so we can keep track of them (making sure of course its not already been reported and/or is not fixed in the latest release)