If you liked "Dungeon Siege," you will certainly enjoy it's sequel... even with it's added level of frustration.
Almost.
The addition of a skill tree to the character development added a new layer of strategic depth to the original "four skills, that's it" development scheme. It also forces a player to specialize much more in order to get the most out of the character, which, from a role-playing standpoint, is much more realistic than DS1.
Having a party of characters to fight alongside the main character makes things much easier than the single-player of Diablo and Diablo 2. In the first run through the campaign you can recruit up to 3 members, either characters or pets, to accompany you.
Also added is an adjustable difficulty level, with each new difficulty unlocked through playing the preceding difficulty, much like Diablo... which is where the sequel really shoots itself in the foot.
First of all, playing through the 40+ hour campaign once is grueling and, factoring in side quests, somewhat confusing. If you put the game down for any length of time, even with the detailed journal system, you can lose your place very quickly.
Secondly, the teleporter system instituted may make it easier to get to previously visited area easier, but the resurrection and save system that came with it are a very unwelcome change. Near the end of the campaign, checkpoints are few and far between, and party death in between means either paying a quarter of all accumulated gold to recover your equipment, or hoping you can run unmolested to the point you fell and getting it all back.
It also means that you can only return at start-up to a town, and not where you saved the game. I don't know about anyone else, but I felt the highlight of DS was the ability to save anywhere, and return on restart where you saved it; forcing you to march back to where you were to begin with just adds an artificial layer of difficulty.
Finally, removing certain inventory helpers was, in my opinion, a horrible move. DS's expansion added a nice button that auto-shared potions among the party: a similar button was badly needed for DS2, but sadly absent.
The Deluxe edition comes with both DS2 and Broken World, the expansion, along with a short story (very dark, but well written) and some videos, wallpapers, and other goodies. The price is right for the games alone, so the bonus content is definitely worth owning.
If you're looking for a good action RPG to eat up several weeks DS2 is an excellent choice. I just wish it had lived up to its predecessor's promise much better.