Yeah, that's what we all thought at first. Unfortunately (and I've found this out the hard way) this is naive.
Moving CCK's functionality into core means no feature releases for (at least) the next three years. Meanwhile, Fields in core stomped the single largest game-changing feature to hit CCK since it's creation: multi-field support. So now, if you're in a situation where you need to delta-sync multiple fields, you have to bail on the Fields API entirely and implement hook_node() or a custom form.
In other words, the grim reality is we've traded 30 extra seconds of work (drush dl CCK) per install for a frozen feature set that is incomplete when compared to CCK 3.0's functionality in D6.
The DB API is also seriously problematic. From a maintainer's perspective this means 100% of the code in any 6.x modules have to be at minimum tweaked, typically completely rewritten. This also means that developers have to memorize two data manipulation models, one of which has fucked up proprietary syntax requirements entirely unlike the SQL it's meant to replace. Not to mention the new DB API leads to rampant code bloat. What was a simple one-line select now takes anywhere from 5-20 lines of OO fuckery if you want to adhere to D7's nebulous style requirements. You even take a performance hit since all of that crap has to be run through additional layers of parsing before it gets cooked down to SQL. This isn't abstraction, it's added complexity with no win attached.