I worked at Goldman Sachs in the summer of 2006. It was a one-of-a-kind learning experience, but I simply wasn't cut out for the hours or the personalities. Added to that, being on the "sell-side" (i.e., you're underwriting and selling securities) vs. the buyside (i.e., hedgefunds etc), means that you're at the whim of demanding and capricious clients. The work was actually very interesting - especially since 2006 was an incredibly busy time in IBD so they had to give summer "real" work. Investment Banking is a good stepping stone into other top-tier finance jobs but if you stay in banking the whole time, it becomes more-or-less a sales job with some basic finance knowledge. It's not for people who care about being good investors.
I worked as an analyst working 70+ hours a week with really smart colleagues at broadview associaties in the early 1990's advising technology companies in mergers and acquisitions. I learned a lot about corporate strategy, valuing companies and technology trends (yahoo was just getting off the ground and the internet was a "new phenomenon"). the job was at times stressful and demanding but I think it was a great place to start my career in finance.