The Banff Springs really is a historical landmark - people from all over the world come to gawk at it and take pictures. But what's it like to stay there you ask? Well - it's pretty good - it won't blow your mind but it's not disappointing either.
The first thing people will tell you is that the rooms are small - this is true, but they're very clean, pretty and comfortable. The beds are comfortable and the linens are really nice. The washrooms are tiny and there isn't much space to spread out your stuff - so make sure you bring a toiletries bag with a hook you can hang up. The shower head has nice water pressure (a big plus on my list) and plenty of hot water. The staff are extremely friendly and helpful, the pool & changerooms were clean & well maintained. On a Saturday night the hallways were very noisy with returning party-goers until about 4am - I wished I had brought earplugs. Other than that I found the hotel quiet and never heard anything from the rooms beside or above me (it was pretty full that week too).
The room service is pricey but so is everything in the Banff Springs - including snacks in the Castle Pantry. I found the little convenience store across the street in the Conference centre a better choice (they really have everything too). I ate at the Rundle Lounge several times and found the food to be so-so (I ordered the steak salad and the greens were long past expired and have mushy-sticky bits on it - I did get a mediocre caesar salad for free about 20 minutes later).
One tip I will give: join the Fairmont Presidents Club - its free and you get lots of little perks when you stay - free wifi, free gym access (usually pretty pricey), a newspaper every morning, upgrades after so many nights etc.