Trail conditions - No micro-spikes/crampons needed. There is no snow on the trail above trail camp. There was a tiny patch (less than 10 feet on pretty flat gradient) between Trail Side Meadows and Trail Camp. It is stained pink in patches due to Chlamydomonas alga. Do not eat it, however much it reminds you of watermelon snow cones on a hot and tiring hike. The water crossings are very manageable. I followed the regular trail and had to cross the two water crossings within the first mile from the trail head. There's lots of water gushing across but enough outcropping rocks to tip toe across. Waterproof boots with good treads will help. The meadow before Outpost Camp has a few crossings too. Rangers installed a new log bridge over one of them as I came by (Thanks!). The waterfall staircase (as I call it) a mile above Mirror lake is gorgeous. It may look intimidating but the rocks are not slippery. Some steps have shallow water and others can be stepped around. All water crossings are no more than about ankle deep.
Weather - I found the weather to be in line with forecasts from mountain-forecast.com. Expected 39-43F at the summit in AM hours and it felt like that. Perhaps a little colder than that due to wind chill. At those temperatures, you will need something more substantial than a fleece jacket. Dress in layers so you can take a few off while coming down as it gets pretty warm below Trail Crest after noon. People in shorts found it to be uncomfortably cold at the summit in AM hours.
Water - Lots of water is available on the way. Major refill points that I found to be good - one within a mile before Lone Pine Lake and then there is the stream by the Trail Side Meadows (between Mirror Lake and Trail Camp). Look out for the wild flowers by the stream. It is a sight to behold. Lake at Trail Camp is popular too. There are a couple of streams on the switchbacks above Trail Camp. The snow is still melting and I do not think the flow rate will dwindle any time soon. In terms of water planning if it helps - I used about 2 liters from trail head to Trail Camp, another 2 liters from Trail Camp to Summit and back to Trail Camp and a final 2 liters from Trail Camp to trail head.
Critters, bugs and animals - Bear sightings (second hand report) in Whitney Portal campground (lock your food in the camp site's bear lockers). A few deer on the way (before lone pine lake and between Outpost Camp and Mirror Lake), a coyote at trail camp on the far side of the lake, and mosquitoes at a few places (I was fine without any repellants). Watch out for squirrels and marmots at Trail Camp. They can chew through your tent if you leave food in your tent.
Gear - Waterproof boots with good tread, dress in layers, sunblock and mosquito repellant, hiking poles, cap, sunglasses, bear locker if camping at Trail Camp (other places have bear lockers).
On Mountain sickness - I used prescription Diamox. Talk to your doctor about what you should do for more advice. Drink lots of water and keep yourself well fed. I did not feel any mountain sickness starting from almost sea level and up and down back to sea level in 3 days.
Rangers - Whitney rangers walk up and down the trail checking on permits and wag bags. Make sure you keep them handy. Hats off to the rangers for doing a great job and all those trail maintainers. The trail is in great shape. Lots of nice people and smiling faces on the mountain. Have fun and safe travels!
