I recently purchased this system at a best buy during a promotion, so I got the system + monster cabling for 500.
I compared the system to the Sony and to the various other systems in the store, and by far I found this to have the nicest, cleanest, deepest sound.
I was considering one levle down, the 505. That system did not have a DVD player, was a 100 bucks cheaper, had a notch down in the receiver but does have a powered sub. In comparing the sound quality, I thought that the 705 was at least 1.5->2.0X better. With the addition of the DVD changer, it's a no brainer. In terms of sound quality, the only systems (in Best Buy) that I found to have higher quality were on the 1000.00 ballpark.
Operation of the system is excellent. Sound and picture quality are noticeably improved. The Prologic II is excellent, makes DVDs completely immersive.
Overall, I have no complaints about the quality of the system. I think this is a super deal particularly if you can get ahold of any dealings to get the monster cables with it (10->50% improvement with those cables at least, I think) the DVD/MP3/CD changer is very nice. Setup on the system is easy with cable+vcr+DVD that came with it+XBox. The XBox has a surround kit that I have not yet researched, but if it works will buy.
Now the bad stuff:
1) MP3 names don't scroll. For 500 bucks, I think this should have a feature my 80 dollar CD/MP3 has.
2) Complex Remotes. I think this is almost every system on this level, but having used a few I think this one is particularly complicated. You basically need to read through the book to do almost anything but the simplest controls properly.
3) Monster Cable Orientation. When I setup my system with the monster theater pack, I noticed on day 2 terrible sound. The intuitive slant downward orientation of the cables was wrong, and they had all slipped out. I had to flip them all 180 degrees. After this no problem, but this was annoying.