It's a mixed bag, IMHO. I stopped playing D&D in about 1993 or so and started up again with 3E. Obviously, I didn't get Dragon during that time period and the style had completely changed, from my point of view. It took me a bit to figure out what of the new material I liked, but I did find quite a bit to like. So, my initial reaction to Dragon in 3E is "different, but not worse or better".
Still, I agree with whoever noted that it seemed to start to decline with issue #300. Other than the latest, I've looked through (in some detail) every issue since then and only #301 and #303 were worth purchase. IIRC, none of the others had any feature content worth my time thumbing through. The exception to this are the Wizard's Workshop articles, which may not be awe-inspiring, but always of some use.
Let's look at #303 and see what I liked and disliked:
p1 Cover art. One of the best since 3E. Unfortunately, that's like saying "one of the least painful kidney stones". I remember when cover art was, well, works of art. Since 3E (maybe somewhat before), the covers have been, frankly, uninspiring. I want to see a finished piece of art (ya know, with a background) that is more action than pose. Looking at the cover art for 306, I'm not sure I totally like it, but it's definitely a step in the right direction.
p8. Wyrm's Turn: Eh, whatever. Mildly amusing, but not something that's a "draw" to me. Every other magazine includes a "from the editor" page. This one is better than most.
pp. 10-16 Scale Mail. I vaguely like the idea that there is a reader response area, but I rarely read it. Sometimes (like this issue) I browse and see if something catches my eye. I wouldn't miss it if it disappeared, but I begrudge the space it takes up less than some other bits.
pp. 20-39 Campaign Components. This isn't the best of the component articles, IMHO, but that's probably because I've only got a minor interest in gladiators. Still, it's a good, solid article. In itself almost worth the cover price. Put succinctly, I like the Campaign Components and will probably buy all that are forthcoming.
pp. 42-47 Prestige classes. Nice. I like the invisible blade more than the others, but you can't win them all. Still, the rules for all are solid and give some good ideas.
pp. 49-53 Optional rules. These are pretty good. I don't agree with all the options listed, but that's fine -- they're options. Still, it's overall a good article.
pp. 54-61 Fighting styles. Eh, mediocre. I like the idea of fighting styles and enjoy seeing some put together. I didn't particularly care for any of those listed, and thought the article ran a bit long. Basically, I like the concept, dislike the implementation. Try again.
pp. 63-67 "Ecology" of the Underdark. Again, mediocre. Not something that increases my odds of buying the magazine, but I'll probably get a bit of use out of it -- or not. Still, I can see the draw.
pp 68-70 Guild Secrets. Above average. Again, not something that I'd wait expectantly for, but I will harvest some ideas from it. I liked this GS better than the others I've browsed, though. Overall, it's a feature that makes sense to have as a regular feature, although I expect that it won't ever be my favorite.
pp 73-78 Fiction. Complete waste of space. I'd be more than happy to never see fiction in Dragon again and this isn't even particularly good fiction. To avoid a tirade on the matter, I'll just leave it at, I oppose the inclusion of short stories/novellas/excerpts/etc. in Dragon unconditionally.
pp 80-86 Silicon Sorcery. Waste of space. Please stop converting stuff from NWN. If Silicon Sorcery is going to be included, then please spend your time reviewing DM/Player aids. Please don't talk about video games -- if I wanted that I'd get PC Gamer. Even in the best of cases, I'd rather not see Silicon Sorcery.
pp 92-104 Wizard's Workshop. Nice. Most WW articles are at least somewhat useful. These are typical. These are a constant, and a pleasant one. Unfortunately, they are never of a quality to really spark an interest.
I didn't mention comics or ads. Ads are a necessary evil. Comics I enjoy, but there are a few too many in each issue.
Okay, so I obviously liked most of this issue. What's different with the others? Obviously, I didn't much care for the content. Since I don't have those issues, I can't do a play-by-play. I'd say that, IIRC, most issues have had some content that sounded like it was okay filler, but nothing that really caught my attension. There were a couple that I thought had nothing be drek in them (excusing things like WW, which as I said is a good constant, but not a buy/no buy maker).
There have always been lackluster issues and always will be. Hopefully, the good outweighs the mediocre. At this point, I'm not sure it does. #306 looks better. Hopefully, the fiends are more than just new monsters -- they'd be better served expanded on existing critters than just adding new ones.