Hotmail tends to treat half my legitimate emails as spam, and let most of the actual spam through. The biggest problem is that fact that it apparently seems to get hacked every few weeks. No matter what I change my password to,I always, every few weeks, open my emails to find myself bombarded with delivery failed notifications for vast quantities of spam that've been sent from my address. It's definitely not a security issue with my PC (done multiple virus scans, and even reformatted a couple of times since it started happening), it's just Hotmail's abysmally crap security. Other than that, I don't have many issues with it, beyond the general slowness of the website when I'm forced to go there to check my junk folder.
I mostly only use it for legacy reasons nowadays anyway (I've registered on so many websites with that address over the years, there's no way I can possibly remember them all to go and change it).