My apologies, I haven't been very active here in a while (work, life, other stuff), so perhaps I shouldn't comment. Nonetheless, I would like to answer.
Today was the first time I've been to SitePoint in a while. I was happy to find SitePoint feels much the same to me as on other visits. I see some familiar faces that were here when I was more active; it doesn't look like there's been a lot of turnover. I see friendly banter and thoughtful questions. Furthermore, there's still many patient responses with very little of the "RTFM!" or "lurn2google n00b" attitude that characterizes many other forums.
In other words, SitePoint is just as good as I remember it. Better, actually: there's even more information. Coming back was like running into an old friend and discovering they're doing really well.
Regardless, I applaud your willingness to consider criticism. Indeed, I think that part of what's kept SitePoint alive so long has been this constant tweaking and examination of the community. In this regard, I think there's some parallels with Slashdot...evolutionary adaptations to the site suggested and selected by a passionate core membership.
As for the commercial aspects, well, I understand. This stuff costs money. In my opinion, however, your commercial side reasonable, tasteful, and context-appropriate. I've found your products useful and informative.
The current model works OK for me. I understand you're trying to find a balance that brings in revenue without making people set up another Adblock Plus filter. That's a fine line. If people are complaining about the intrusiveness, there might be other options.
On Slashdot, for example, they give people the ability to disable or limit advertising if they're reached a certain level of participation in the community. It's related to their notion of "karma" there, so it's not simply quantity of posts, but factors like post quality, length of membership, etc. Perhaps this might be an alternative?
Or what about a tiered subscription option...visit, more ads; join and participate, reduced ads, quality participation or send us X amount, and lose the ads. Send us X amount more, and get all of our books. Just don't punish people with really obnoxious advertising if they don't pay, of course!
Yes, some people won't be happy with any advertising, product sales, or anything that suggests SitePoint might have commercial interests. Are they simply griping about the advertising, or do they have any practical alternatives? Is there another model (besides donation- or subscription-based) that scales effectively?
TaliaJ / TaliaJ2 (Been here since 2005; first account had some sort of unresolvable password issue :()
/All this said...I'm sorry, but the t-shirts were a real yawn.