How far pre-compiling a website or project in VWD is safe ?
I know that Reflector can retrieve the whole thing again (as it will be IL at the end of the day), and I heard that obfuscation won't go so far (not sure) there is tools to deal with obfuscation.
Is there a good solution to guarantee that clients don't get to the underlying Solution architecture, and algorithms ? [plz consider the case where the client is a pro or an IT company]
Clients (as in users of your site) will not certainly get this far. Unless the server gets somehow hacked and makes the directory with your binaries visible.
What you should is to add custom error pages, so that when something crashes the users don't get to see the Yellow Screen of Death with the call stack, code snippets and your SQL queries.
If you're that paranoid, host it yourself. If you really don't trust your customer, don't give it to them. .Net is a reflective framework, there will always be scope for reverse engineering.