Never saw infinitely respawning vehicles in campaign. Vehicle battles are an earmark of Halo combat and they're one of my favorite parts of the series. I like to go on foot through many of the portions of the campaign, but if I can use a vehicle I will always, hands down, grab one because usually they're not only more fun to move around with, but they pack some kick ass weaponry and functionality.
The vehicular combat in Halo 2 was one of its saving graces. The worst levels or worst parts of levels for me were never the ones which had vehicles, they were always the ones which were on foot, through narrow, linear and predictable corridors. This the reason most people absolutely love Outskirts, Metropolis, Delta Halo, Uprising and The Great Journey.
The best parts of the Flood levels were when we faught against them in the Quarantine Zone on vehicles. The best part of the Heretic levels were in the Banshees. Vehicles, their function, and their ease of use in the series changes up the combat significantly and they're a reason Halo was set apart from many FPS' (not all) back in the day and still to this day.