Long time BG player, I remember going out in the snow when it launched WAAAAY back in Dec of 98 to ensure I had a copy on release day...4 CDs of content, long install...so worth it. I've played through the game (and its sequel) many times, with each different class, difficulty, etc.
When EE launched, it was an insta-buy. The game tracked my play throughs (sort of) with achievements, very awesome! The graphics were improved, the gameplay smooth as ever, the new companions felt right...just an awesome experience. I again played through each game multiple times.
Then the other shoe dropped...NEW BG CONTENT!!! Couldn't wait to finally bridge the gap between BG and BG2 with Siege. I was again first in line with a preorder, VERY EXCITED.
But for some reason, I have a very difficult time finding immersion in the game. It felt non-congruent with the other two. The companions felt 'weird', the story didn't make any sense, and your progress didn't really affect the BG2 story (besides xp gained).
To this day, I haven't been able to play though siege in it's entirety. I'd have preferred to 'start fresh' with a prologue to a new BG story than attempt to bolt on more content to a fairly complete game. It sort of felt like trying to rekindle a relationship with someone when it ended for a good reason...kind of exciting at first, but you quickly realize it's awkward and forced.
My advice to Beamdog...continue with the EE concept, IWD, BG, and NWN are brilliant. However, when adding new content, start fresh with a new story, but utilizing the same awesome game engine. I will likely not buy another product like siege, bolted on to a current legendary story.