thanks for your comments - it is useful to know what the SilverStripe project should focus on. You'll be pleased to know that the issues you raise are areas that we've been working on in serious ways recently:
Right now we're a few weeks away from having a 450 page book on SilverStripe for developers that will greatly improve our documentation, (see http://www.silverstripe.org/silverstripe-book/) and it will explain why our templating language is intentionally simple.
The work on the upcoming 2.4 release relates to performance, and may help in terms of separation of CMS/Sapphire (and removes the jsparty folder) and solving other bugs you're encountering. In terms of supplying us with patches/fixes, thanks very much; being an open source project we depend on that. In terms of your slowness and bugs, please continue to raise the issues in detail at open.silverstripe.com so that they get visibility and can be worked on by the core team or other community members :)
Sigurd, SilverStripe.