Andersen is pretty decent. With the way Miami plays defense, a lot of times they funnel penetration into help defense, and it's an area he probably excels in, coming from the weak-side and contesting penetration. Pick-and-roll defense, they probably have more liberty than most teams to switch everything, and Andersen is mobile enough. Guy runs the floor well, and finishes pretty well near the rim on lobs, put-backs, and gimme's. Those are the only kind of shots he'll be expected to make, as a recipient of others' penetration.
Spoelstra and the other players don't ask much from their bigs outside of Bosh and Haslem, they actually dumb down the game as much as they possibly can for them. That's all they ask for, hustle plays, hitting the boards, denying penetration, contesting shots, help defense, etc. With the veteran's minimum, that's a welcome addition.
Strength and size though is a problem. It's not something they have to worry about against most teams, but they'll have to address it when they go up against Andrew Bynum and Roy Hibbert, potentially in the playoffs on the East side of the bracket.
I actually like Harrellson's game. Although, I only watched him during March Madness, I was impressed with his mobility and motor for a guy of his build. Someone will probably get waived or bought out, and ended up being a "value" pick-up for them. There's no rush for the Heat at the moment to go and sign someone, stuff happens during the course of the regular season, as you know.
At the end of the day, we're talking about players for the veteran's minimum. We can get into these technicalities of whether the Heat can sign a center "better" than Asik, but my original point a couple of posts ago was, yes, that I agreed with you that center will always a be a need based on their salary structure. Even though they only have the veteran's minimum to offer now, I still believe they can find a serviceable center, at a better value than Asik was, given that they're the defending champions, and will always be contenders for years to come barring injury. You're free to agree or disagree, I don't really have much more to add besides that.