Not none. The downsides are moderately decreased in my experience. I’m not sure the amount in tea, I suppose it varies greatly, but I’ve tried several different l-Theanine doses and caffeine mostly still feels like caffeine, just slightly modified.

In my experience, many of the negative effects are greatly reduced. When my dad first brought back a box of PG Tips from a work trip in London, I discovered I could drink like, ten cups and still function. Only moderately burned out.

If I had drank the same amount of coffee I'd've needed to lay down. It was great for all nighters playing Halo multiplayer.

All this time I thought tea's superiority was due to it having "more hydration" or something. This is so interesting to know!

In my experience it’s been that tea gives me far less anxiety, but still a nonzero amount. It doesn’t wipe it out entirely, but it reduces the physiological symptoms of anxiety.