As a starting point, it's hard to not like Coach McMillan. Many coaches seem incapable of getting their players to play hard for them these days, and McMillan doesn't seem to have that problem with Portland. Also, as the post says, he's been really good at taking advantage of the Blazers' strengths and making a very efficient and high percentage offense. The fact of the matter is that he took a talented team and won 50+ games two years in a row, which is not easy. Overall, I think that the Blazers should be very happy with Coach McMillan. I hope that they don't get rid of him anytime soon.
Having said that, there are some warning signs on offense and defense.
Offense first: the Blazers have had success in the regular season with their offense. I'd argue that this is a function of the fact that most teams don't have a chance to prepare and game-plan very much during the regular season. The Blazers' offense is efficient but predictable (Roy high pick and roll, Roy isolation, Aldridge isolation in the post, stuff like that). We've seen some evidence over the last two years that this won't work in the playoffs. Obviously there's been a lot of other things going on in these series. The team that lost to Houston was young and inexperienced, and last year's team was missing it's best and most important player. However, both Houston and Phoenix showed that they could kind of tune into what Portland was going to do and stop it by forcing Portland to go to other options on offense. The recipe is pretty simple: double team Roy, force him to give up the ball, live with Aldridge scoring, and bet that none of the other guys will be able to carry the load. Portland is a good team, but I think they'll have to be more diverse on offense to have success in the playoffs.
On defense: the Blazers haven't been very good defensively. They have rebounded very well (very very very well). Rebounding and the slow, efficient pace that the Blazers play at have masked the fact that they're not a good defensive team at all. The Blazers have good individual defenders in all three centers, Batum, and now Matthews, but I think the problem has been with the system more so than with the players. I think that McMillan's defensive schemes just haven't been that creative, and I would bet that there hasn't been that much emphasis on defense in the past. There's a lot of talk about emphasizing defense this year, but the Blazers will have to walk the walk before I believe it.
I hope that Coach McMillan can grow this year and address these problems. I'm excited that we have new assistant coaches, and I hope that they will bring a new perspective to both sides of the ball.
Feel free to share your thoughts about Coach McMillan in the comments.