So all you want to know is 'Should I bother upgrading?'
Here's the differences:
1. Some of the character classes have been overhauled. Barbarians now aqcuire abilities in a far less lumpy manner; there's a few new abilities for Bards; Monks have been tweaked, including at low level, as have Paladins; and Ranger abilities have been substantially adjusted. Of the other 'traditional' classes, only Rogue has been played with, with improved aptitude with traps now added (Trap Sense proves helpful to players and DMs alike). ALL of these adjustments are improvements.
2) Skills have been mildly adjusted. Animal Empathy has been removed as a stand-alone skill, and Alchemy now comes under Craft, and the rarely-used Innuendo has vanished. Intuit Direction and Wilderness Lore are no longer skills but Knowledge checks, Pick Pocket is part of Sleight of Hand... you get the idea. Most importantly, which skills are class skills went under revision, and yes, Initimidate IS now a Fighter skill. These may seem like superficial changes at first, but for fans of Roleplay rather than Gaming, these will be important.
3) Some new Feats. At first, the double-page spread of listed feats looks like a massive expansion, but in fact most of the new ones are the kind of feats that merely boost a couple of skills or saves by 2 each. Players are unlikely to find these useful, but they are helpful for DMs padding out specialist NPCs.
4) As D&D moves a little closer (optionally, of course) to miniature gaming, the Combat section has been expanded with a lot more illustrations.
5) A (very) few new spells. Many of the spell lists look slightly longer, but on closer inspection, a lot of these are spells for other classes that have migrated (for example, Bard 1st Level spells expand from 20 to 26 on the list, of which only one - Lesser Confusion - is new to the book. The rest have been poached from the Wizard list). If you crave more spells, your best bet is to buy the softbound 'splat books' - Tome and Blood, Defenders of the Faith, etc.
Conclusion: In many hobby shops, the price-to-substance ratio of this upgrade would deserve to be marked down. However, the online price makes all the difference. Buy it.