You know I did have the 9 inch vesion of the Jelco tone arm in the house for an extended loan when I first got my Serac, I was waiting for my String Theory arm to be built. Truthfully, I saw nothing about the Jelco that was terribly impressive. I know it is kind of a favourite due to its affordable price, but I see nothing that distinguishes it from....say the Technics arm that comes with the 1200. I think the 124 deserves a better arm that the Jelco, but then again I am not a fan f the SME 3009 either.
As far as the other forum opinions, the only thing you can really do is experience one for yourself. get a chance to listen to one, or spend the money and takes your chances. I learned a long time ago that others opinions are filtered through their personal biases and desires. A 124 is not for everyone, but for those who enjoy idlers it is a good one.
I had a minimal amount of money in mine when I gotit up and running. Probably about $400 or so between maintenance items and the ADC tone arm. With a MM cartridge I thought is was decent but not exceptional. I ran an AT 125LC, a Signet TK5ae, Digitrac NE 200, in short nothing I could get excited about. When I put the Cleraudio in place, well things really turned the corner and I could get excited about this table. I find it good enough to be worth spending serious money on, and the table is worth the $2500 Clearaudio and probably an arm in the $1K range. but that is just my opinion. But the table does have to be given a bit of maintenance to ensure it is operating properly.
Regards
Mister Pig