This is an immensely popular trailhead for a few reasons: It's convenient (a free RMNP shuttle drops you right there), it's in a great location (from this trailhead, you can hike to a ton of great sites: Flattop, Hallet, and Otis Mountains, Odessa Lake, Fern Lake, and Bierstadt Lake are among the popular destinations), it's a super easy walk (it's a nice loop, very short at .6 miles, with no incline to speak of and lots of shade, plus many benches to stop on to rest or observe the chipmunks and other wildlife. The trail is paved. When we've flown in in the past around lunchtime, my family and I always use this as a mini altitude acclimation. It's nice just to get out in the fresh air and look around. The walk takes us 25 minutes tops, and that's including multiple photo stops).
Most importantly, this trip is a scenic one. Bear Lake is beautiful. It has great views of Flattop and Hallet in the background. You'll definitely see some birds and chipmunks.
Another plus: restrooms are available right at the trailhead.
A drawback: Because of its immense appeal, this trailhead is almost always crowded. Don't expect a peaceful and serene spot to enjoy the scenery. It's still extremely enjoyable. If you're hiking in RMNP, you'll most likely find yourself at Bear Lake Trailhead for some hike or another.