I've found that megapixels can be as much of a hindrance as a benefit, particularly in cheaper cameras. In the last year Canon has rolled back the number of MP's on some non SLR camera sensors (like the SX30is which my wife uses as her holiday camera has been superseded by the 40is which has 2MP less). I can understand why, as images were lacking vibrancy and brightness (without a lot of post processing). As the pixels were being too tightly packed onto the sensor the available light to each was getting less and less.
In SLR cameras with larger sensors it's not such an issue, but my experiences (I run a 5.66MP Nikon D2H and an 18MP Nikon D7000) are that particularly when shooting in RAW mode with a decent pro series zoom or prime there is very little to tell between the two cameras. Most of the losses are realised in the lens, and actually the higher MP D7000 is more ruthless about exposing lens limitations (abberation / vignetting) than the D2H. The D2H is a CCD sensor, whereas the D7000 is C-MOS, so the D2H suffers a bit from noise in low light situation, and you can't crop and retain detail in the same way as you can from the D7000.
That said, the D2H is nigh on 6-7 years old, and it's AF detection / reliability is second to none. Whilst the D7000 has over 50 focussing points (against D2H's 11), it struggles like hell to focus in really low light where the D2H nails it every single time. Hard to believe in 7 years they can't significantly improve contrast detection AF on the newer tech. And as you say the motor drive in the bigger pro cameras mean you never miss a shot.
Think you made a good choice with the EOS-1i, it's a bulletproof piece of kit, totally dependable, and you'll get shots with it that the D30 couldn't even capture!