Yup. I think I learnt a lot in these four years, sometimes I look back and wish I had focused on startups earlier but I realize I still had a long ways to go back then.
I finally quit this past May and joined a former co-worker on his new startup, so it all worked out in the end.
I have a similar story -- 5 years at a company where I ended up being bored and not caring about the work. But I learned a lot during those 5 years, and was able to take advantage of several opportunities that may not have otherwise been available to me.
And like you, I'm now at a startup, that I love (heh, most of the time), where I've been for the past 11 months. It's all about timing, I guess.
I finally quit this past May and joined a former co-worker on his new startup, so it all worked out in the end.