The conventional wisdom seems to be that the Blazers need a starting point guard who is a better "fit" alongside Brandon Roy. "Fit" is generally short hand for "a guy who shoots better." I find this whole line of reasoning annoying, not because it isn't true in some hypothetical sense, but because it leads fans to undervalue the things Andre Miller does well and to covet players who are inferior to Miller.
Consider this: Basketballvalue.com keeps track of the adjusted plus/minus of every 5 man lineup in the NBA. In other words, these are not just raw plus/minus numbers, but numbers adjusted to reflect the quality of the opposing players as well. It allows for a number of interesting comparisons. For instance, among the 11 Blazer lineups who played more than 50 minutes together last year, the lineup with the best adjusted plus/minus was this one:
Miller-Roy-Webster-Aldridge-Przybilla (Adj. +/- 17.67; Off. rat. 113.99, Def. rat. 93.71)
The worst of those 11 lineups was this one:
Blake-Roy-Webster-Aldridge-Przybilla (Adj. +/- -17.91; Off. rat. 95.14, Def. rat. 105.98)
As you'll notice, the only difference between these lineups is the person playing point guard. Yet despite the supposedly better fit Blake provides, the lineup with Miller was WAY better.
I realize that this one comparison isn't definitive proof that the Blazers are better off with Miller at point guard than, say, Mo Williams. But I think it at least provides grounds for caution. Basketball is indeed a game of chemistry and the way players fit together matters, but you don't want to let such considerations blind you to other factors, such as the overall talent of the players in question. Miller may not be the perfect fit alongside Roy, but he is a very good player, and he makes up for his lack of outside shooting by being really good at other things, such as passing, rebounding, and drawing fouls. If we replace him with a shooter, there's no guarantee that the tradeoff will work out in our favor.
If someone like Chris Paul suddenly becomes available for a reasonable price (which I find unlikely), I'm all for making that trade. But it is not at all clear to me that a lot of the other names that are often bandied about (Devon Harris or Mo Williams, for example) offer an upgrade over what we have in Miller.