70-300L is a good lens, not too heavy, highly versatile, and nice image quality. On crop bodies like Ti's you will also have great reach. Contrast is awesome, and the IS is new and fast. It lags just a bit on the longer end at 300mm...but that will be really nit-picking.
300L prime of corse would beat it in image quality, but you will lose the versatility of this nice zoom and ability to frame more or less with wild life. Like everything in life, it is always a compromise.
It has a stable spot in my collection and while I periodically threaten I will get rid of this or that lens, this zoom has never been a candidate for unloading if that says anything. Well behaved, affordable, underrated gem.