MSE might catch about 80%-90% of malware that's out there. Is it worth having? Sure, it's way better than nothing. if you have no other Anti Virus program with a higher detection rate, then I may stick with that instead of MSE.
I'd say its sufficient. I've had maybe 3 browser attacks which MSE all caught over the last few years. However, on my a friend's computer, something did get installed which MSE did not detect, and we had to download the trail edition of Malware bytes to find/delete it.
If you are somewhat intelligent about what you are doing, MSE is more than sufficient. If you are the typical idiot Facebook user and click every pop up in a browser that says "you must install this thing right now." Well, you may want something a bit stronger.