Go for it! I think you will learn a lot, and it seems like your expectations are calibrated well.
Source: wrote a browser[1]. I enjoyed it and learned a lot. My motivation for starting it is that the open source browser landscape was bleak at the time. There was khtml, which seemed fairly solid, but that was KDE and I was firmly in the Gnome camp. Mine was very fast and lean, but wouldn't scale to embrace what's now considered the basics of a web browser: JS and CSS. Motivation tailed off sharply when Mozilla announced they would be open sourcing their browser. If I had known it would take them over 4 years to ship Firefox 1.0, I might have kept at it.
Gambatte!