What's your experience of SFDX ??? What are the issues which you faced ?? Any best practices or design patterns you created ??

Way better than the alternative, which is the old metadata API driven stuff in Eclipse.

Biggest advice I have is to create a script to set up a new scratch org and install any dependencies / config you need in one hit, as you'll be doing that often. If you hit any problems, you can then just get rid of your current scratch org and spin up a new one immediately.

Always use with version control, and commit early and often, as that makes it much easier to use tools like git bisect to find a problem later on.

Oh, and make sure your config file is set to disable caching on all new scratch orgs you create, otherwise it'll cause all sorts of weird issues later on (or at least seem to!)

Thats great advice to disable the caching, and also other day i was backing up a my org data in a scratch org to learn the migration steps spent whole day in fixing the errors, so now i always use features like person Accounts,defaultworkflowuser, chatterenabled, authorapex etc, that helped me a lot

That moment you see SFDX and go "wow I'm not alone in here"

I'm looking at doing scratch orgs in pipelines (ci/cd) at the moment to automate all the config required to spin up an instance.

As it stands now, a new refresh can take 3-4 days for a sandbox due to 3rd party apps needing to be set back up each time as well, got to love data as config and a lack of a user manual.

Outside of that, just being able to write your code in vsCode and then push/pull it to/from the current org is enough for me to not use that devConsole or Eclipse.