Tabs become pretty much unusable once there are too many open. You can't read the text, and the close box goes away. And if the close box is still there, I find myself clicking it by accident because the tab is too small.
I'm used to using Eclipse, and I like how they limit the number of tabs shown based on how much space is available. This way, you can always read the beginning of the file name, and the close box is always visible. When there are more tabs that can be show, a little menu shows up on the right. The menu shows the "shown" tabs in bold", and the ones that can't be shown are normal. You can then show a tab by selecting it from the list, and another visible one will take its place.