Do you think these are necessary to make good improvements? Or can you go old-school just training hard, with equal benefit?

Yes. You have to have one.

You can get one for $10 at Walmart.
Why not.

The simpler, the better, IMHO.

I'm a data junkie, can't imagine not having one... but necessary to improve? If that's the bar, I'd say no, probably not.

Get a Cateye Strada Cadence.

I got one (actually two adding HR & Cadence) to help track progress (just waiting for progress to ACTUALLY happen).
It helps me during a ride to stay honest in my efforts...feedback spurs me on.

A HRM with a ride timer has been more beneficial for me than a cyclometer.

As my old friend used to say, "No brain, no pain"

Agreed. I'm trying to get a 705 for Christmas because I'm a data nerd. That being said, the only functions I really use are my HRM and the ride time on my cycle computer. The other things are just nice add-ons.

The only things I actually train by are time and heart rate. Once I have power all I'll train by is time and power. The rest is just fun data.

Then why not get a 305 - what's what I use. The real time GPS is just to fancy for me.

You can't add power to the 305...

What umd said. As well as the fact that the 705 is so badass. I'll use the directions to stop from getting lost, which I do frequently. I'm also looking forward to having cadence, HR, power, speed, elevation, etc all on one chart. Looking at how all that works together I think will help make me a better racer. I'm hoping to learn things about how spinning helps me, looking at how well I climb/descend, checking HR against speed and power, etc.

But the MAIN reason for getting the 705 instead of the 305 is the ANT+ capability to add power next summer when I get a meter.

Does the 705 give total ascent of a ride? I miss that feature in the 305. (I use the Forerunner 305, BTW, as I cross-train with distance running.)

The Edge 705 and 305 both give total ascent. The Edge 605 and 205 do not.

I've also got a simple Polar HRM.
BUT, I do want a powermeter of some kind.

Ah thanks. I think that Forerunner 305 gives total ascent as well in the PC interface form, but I never download my rides to the PC.

The Training Center software will add the elevations up and arrive at it's own total ascent regardless of whether or not the unit kept its own total. The main difference is that the 705 and 305 have the barrometric altimeter and accept accessories while the 605 and 205 do not.

Yes, as long as the computer is a Powertap, SRM, etc. Other than that, it's somewhat optional. All your body knows (and adapts to) is stress and duration. If you get hung up on the most meaningless of cycling metrics (average speed) a computer may do more harm than good.

I can't imagine riding without SOMETHING telling me how far and how fast I went. Granted, you could figure out your mileage with google maps, and keep time with a wristwatch, but like others have said a simple cyclocomputer (i.e. cateye wired models) can be had for $30 or so. For that little money (less than a tire or a couple weeks worth of clif bars), I don't know why you'd NOT buy one.

That'll never happen if you keep buying things that make you go fast without making you fast.

Cyclists were training well before cycling computers and did just fine so it isn't necessary, they just provide information on your ride and performance.

Hey guys, I have been using a very simple Cateye computer for about 3 years and I am looking to upgrade to one with cadence and heart rate. I would like to stay under $130 if possible (this is coming from the money I get from my grandparents at christmas). What would be a good option? Thanks a lot.

I know a kid that pretty much only uses a watch and he is rather swift.

I had a Polar CS100 that had HR and cadence that was in that range. It was wireless, so setting it up was very easy. Of course, that opens up the chance of interference, but I never had a problem. That kind of stuff is really a factor of where you ride. Urban areas are notorious for scrambling wireless data, whereas rural rides are generally just fine.