I've done this hike several times, the lake itself is a great spot for backpacker's looking for a nice camp spot, and there are several other well marked camp sites up the creek within 50 yards from the lake. It's a perfect in and out day hike as well, and since you are on the Pacific Crest Trail you can pretty much turn around whenever you feel like it. Depending on which access point you use, you will hit a fairly moderate elevation gain, and more involved techical hiking (depending on the weather) about 8 miles in as you are climbing up Table Mountain. If you are up for it, it is well worth the views.
The lake itself is only 2.9 miles in from the Bonneville Trailhead parking lot. The alternative starting point, (used mostly by PCT through-hikers) is just west of the the northend of the Bridge of the Gods. I usually park my car in the parking lot at the northend of the bridge, where the local honey farmers sell their goods. I can't confirm that this is "allowed" per say, but there are no "no parking" notices, and I've never had a problem. From there you walk to the trailhead, and the lake is about 4 miles in.
Regardless of which entry point you decide on, the hike itself is pretty simple, very family and dog friendly. You lose the sound of the freeway sooner than you would think as most of the hike is heavy forest, (which makes it nice and cool in the summer months). The only issues we had on our summer overnight trips to the lake were the clear cut sections in direct sun, where the dogs got overheated pretty quickly. Chloe (the bassett) decided she was done walking for the day by sitting down in the middle of the trail and refusing to move when we were about 100 yards from the lake--loud and clear Chloe! She got a free fireman carry the rest of the way. We learned our lesson that maybe we need to take a little break before the clearcut sections to let everyone catch their breath and pound some water!
There is a wonderful campsite on the lake, with a huge fire pit, and a little private trail, you feel very secluded, and it's one of my favorite places to camp in the Gifford Pinchot. Others don't find it so "secluded and lovely", because of the view of powerlines and logging roads on the south side of the lake. Granted, it's not the most breathtaking view, but at least you are looking at all points of entry on the lake, which gives you a sense of security.
The lake is absolutely freezing, most of the time, but still worth a dip, and if you are savvy, a rod for the golden trout.
Several years ago, while doing the hike with 5 other PCT hikers, we saw the very large back end of a bear, approximately 2 miles in from the Bridge of the Gods access point. It was very exciting!
Here's the PHFG's page, for directions and more details
http://www.portlandhikersfieldguide.org/wiki/Gillette_Lake_Hike
At the Bonneville Trailhead Access, leave your car empty and unlocked! Lots of break ins in this parking lot day and night!
Looking south during the last clearcut section before the descent to the lake
Best fire pit ever
View of the moraine while heading down to the lake
Tim exploring the different uses of the backcountry "Buff"
Heading back up the next morning
Notice the powerlines, this picture is taken from the logging road before you start the trail down to the lake.
That dang floatee never disappoints.
PCT markers on the trail.
