Earlier today Apple quietly updated its online store to include upgraded MacBook Pro models, which feature improved Sandy Bridge processors, more storage, and other tweaks such as better graphics for the 15-inch and 17-inch Pros. As the rumors suggested in the previous weeks, this is indeed a minor refresh for the line that doesn't yet come with Bluetooth 4.0, rumored to be making its debut on the MacBook Pros but still nowhere to be seen in the product's Tech Specs page.
First off, the late-2011 MacBook Pros (the line was last updated in February of this year) feature improved processors: the 13-inch model goes from 2.3 GHz Intel Core i5 and 2.7 GHz Intel Core i5 (both dual-core) to 2.4 GHz Intel Core i5 dual-core and 2.8 GHz Intel Core i7 dual-core; the 15-inch model jumps from 2.0 GHz Intel Core i7 and 2.2 GHz Intel Core i7 (both quad-core) to 2.2 GHz quad-core Intel Core i7 and 2.4 GHz quad-core Intel Core i7; last, the 17-inch variation has been upgraded from 2.2 Ghz Intel Core i7 (quad-core) to 2.4 GHz quad-core Intel Core i7.
As for storage, the MacBook Pro 13-inch now starts with 500 GB or 750 GB of internal storage (up from 320 GB and 500 GB for the previous base configurations), whilst the 15-inch and 17-inch models haven't seen any storage upgrades. Graphics, however, have been upgraded in these two models, with the 15-inch now getting AMD Radeon HD 6750M and AMD Radeon HD 6770M alongside the Intel HD Graphics 3000(previously, the 15-inch got AMD Radeon HD 6490M and AMD Radeon HD 6750M) and the 17-inch now available with an AMD Radeon HD 6770M with 1GB GDDR5 (previously AMD Radeon HD 6750M 1 GB).
The late-2011 MacBook Pros are mostly a CPU and GPU upgrade, perhaps in preparation of the big line refresh that's been rumored for quite some time to be on track for 2012. Prices are unchanged from the early-2011 models, and you can find the refreshed line on Apple's online store now.
Full-size comparison chart here.