First, the short answer. No, not for normal speeds (avg under 20 mph).
Now the long part.
Even at 22 mph not really, at least not for me (250w FTP on a good day). They make a noticeable difference once you're sustaining (even for brief amounts of time, 20-30 seconds), 30+ mph. For me that means less than a minute, but if I can go really fast for a minute, I really like it
Incidentally you're looking at 1600 grams difference. That's about 3.5 lbs at 454 grams per pound.
First, make sure that the 5 spoke wheel is really aero. If it's the Aerospoke wheel,
it's not aero. It's slower than a lot of wheels out there. If it's the Mavic 5 spoke or similar... well, now you're talking. But it wouldn't be 2900g.
Regardless of the wheel, 2 lbs is about the difference between my "non-aero" HED clinchers (Bastogne) and HED aero clinchers (Jet6 front, Jet9 rear). The Jet wheels are aero, like truly aero.
Having said that, the weight difference, to me, at solo training speeds in slightly rolling terrain (big ring hills), is noticeable, and at my sub 20 mph avg speed, the aero benefits are negligible (i.e. not noticeable).
However...
I really like going fast on the bike. I live for going fast. So I'll struggle with heavy wheels for 30 minutes if it means I can go faster for 30 seconds (compared to going 30 seconds without the aero wheels).
I will first take into account safety (so, for example, I'll think about it before going out in a hurricane on dual TriSpokes, although I've done it because I couldn't resist the idea of a 50-80 mph tailwind). If the wheels seems safe, I'll consider them. I won't use an aero front wheel if I think I'll be descending much faster than 45 mph (50-55+ mph). At that speed I usually tuck, and when I tuck I'm more vulnerable to sudden crosswinds and such. Aero front wheels become a liability at those speeds, in a tuck.
If I'm not tucking then I'll use an aero front wheel, even if I think I'll be going fast (45-ish) anyway.
I noticed a huge difference in acceleration effort with the extra 2 lbs on the wheels. Since the hubs are identical between the two wheelsets, and the cassette is virtually identical, it is the rims, tires and tubes that make the difference. I have comparable weight tires on both wheelsets, literally the same brand tubes, so it's the rims. The aero rims weigh more, a lot more, and the weight is towards the outside of the rim, the worst place to be. I pretty much used up my legs in 2-3 hard jumps with the aero clinchers versus the non-aero clinchers (this on the same course, flat, 3 turns, windy, race, so jumps from 22-25 mph to 30+ mph as hard as possible).
For training I prefer the non-aero wheels overall. But if I'm going out thinking I'll feel good (i.e. my schedule leading up to the ride means I should be riding reasonably and relatively well), I'll go out with the non-aero front and aero rear. This gives me the most stability (aero wheels up front reduce stability in any kind of wind), some aero (rear wheel is about 1/3 of aero wheelset's gains), and less of the 2 lbs weight penalty. Finally, I like the rear Jet9 simply because I have an 11T on it, and I'd like to think I need it on the fast bits (right now that means downhills or when chasing big vehicles since I rarely need even a 12T on the flats in the fall).
If I had one pair of wheels to use (and I make this choice every year when I go to my SoCal training camp), I bring either non-aero clinchers or moderately aero (46 mm) carbon clinchers. In 2011 I'll bring just the Bastognes (non-aero), but I'll put the 11T cassette on the wheels before I go out there (for sustained, tucked, over 45 mph descents). I'm debating bringing the Jet9 rear since the bike will be even faster, but dragging that weight up a climb for 2 hours will hurt (descents aren't free).
cdr