1st things 1st: Get a permit! Ranger at Muir Camp is super nice and helpful.
Do note that solo climbs are NOT allowed, and you'd have to pretend that you are at least 2; which also means that you are paying for 2 permits... yours and your virtual friend's. That is $44 dollars/person if you are older then 25, $31 if you are not!
I started the climb around 11:30 am at the Muir Camp (10,080 ft). If the weather is any helpful, the scenery is hands down fantastic: Mt Helens is visible. I got to the Muir Snow Field Camp around 4 pm... not because I am dangerously slow, but rather because... well... it is just worth taking your time... looking around, snapping pics... and just enjoying this portion of the climb (which at this point is more of a hike).
Once at the Muir Snow Field Camp, expect -especially in July- to find anywhere in between 10-15 climbers camping.
A good 6 hours of sleep later... geared and pumped up... I started the actual climb. For as long as night time prevailed, the headlamps ahead and behind me provided quite the spectacle...
Expect crevasses... LOTS of them. Most are "jumpable"... others required a little detour, mostly because I happened to be alone, not roped up... and not willing to take a chance!
For about an hour, the slope is "manageable", but about 30 minutes after the cathedral Gap, it gets fairly steep...and altitude sickness starts kicking in!
Zigzagging... I did. At times because my legs felt tired... others because it was the only way around the large crevasses.
As the sun started coming out, I looked at the GPS... I had covered about 4.5 miles since Camp!
I arrived at the rim around 10:15... about 2hours later than what I planned... Disappointed I wasn't, but I realized that the zigzagging, while allowed me to rest my legs a bit (and probably avoid major bouts of altitude sickness) cost me quite a bit of time!
The weather had been so far nothing short of gorgeous...
Shortly after, I made it to a super flat surface... what a relief for the legs! A short lived relief as the summiting portion comes up pretty quickly.
I summitted at 12:30.
On the way back, I glissaded most of my way down.... and made it to the camp at around 4 pm. I could have probably made it to the trailhead that very same afternoon/evening... but with achy feet, I decided to spend me another night and head back the following morning!
God's honest truth: Maybe it was the weather conditions (ideal), maybe it was the fact that I climbed Solo (at my pace and no drama), but Rainier turned out to be easier than some other peaks
(edit: Fellow summitpost user Scott pointed to the fact that solo climbing IS allowed, providing you get permission from the Park Service. An 44 dollars oversight! :-))