You'll probably get lots of different opinions about Ashbridges. Since it's close to home for me, I like to go there when I have limited time to spend. It has easy parking and you can be in and out with a few good birds in 30 minutes. In the winter you can find a few good ducks in the harbor and you're almost guaranteed some Common Redpolls on the most Westerly point. During warbler season you can sometimes find numerous species in a fairly small area. I like to walk in from the parking lot along the trail that's right up against the marina fence. Songbirds can sometimes be found starting in those evergreens, then all the way along the path to the little beach area at the end of the marina which usually has the best concentrations. Depending on wind direction, you might also find a few birds on any one of the four points. You should also check the big beach on the east side where you'll see a grassy area that may have shore birds depending on conditions (looked like a pair of Killdeer nesting in there last week).
If you don't live in the area, I would not consider Ashbridges to be a worthwhile destination on its own (unless of course a rarity has been reported, like the Eared Grebe). But, if after a visit to the Leslie Spit/Wet Woods you still have time to spare, it's sometimes worth the three minute drive down the road. I've done this myself numerous times, and often pick up an extra few species. Like many other Toronto parks, expect to find a lot of dogs.
-kris 
co-sign.
i like biking there. or, if you don't own rubber boots, it is great.
for some reason, i've had incredible birding there after lunch. usually, lots of activity.
i would disagree with Kris, though, about it not being a destination. 2 years ago, i counted a dozen scarlet tanagers during the spring. the other nice thing about the park is, if you are lucky, the warblers are at eye level. i've had a Blackburnian 8 ft above me. i've had Magnolia warblers 5 ft in front of me and at chest level. i've watched black-throated blues and chestnut warblers at eye level, again, at 5 feet in front of me. now, i've also had great luck at the Wet Woods and, if you're lucky, you'll get visits at eye level as well. but yesterday had a lot of palm warblers that were 20 ft in the air.
the areas to see birds at ashbridges is basically everywhere on the periphery. in the trees right at the parking lot, i've seen Cape May warblers. the path Kris talks about also shows warblers, but it isn't good for photos unless the warblers fly on the outside edges of the trees. there are some trees in the middle that also yield warblers. but the sweet spot, depending on the winds, it the beach on the southwest end. you will see quality, not quantity.
