Others have already said that it's a community project and so YMMV with respect to older phones.
I have a Samsung Galaxy S (the first one). Since this phone has quite a following I got very lucky: CM has continuously been releasing updates for it, even though it's a very old phone by todays standards. I've been using CM7 on it, now have CM9 installed and am in the progress of upgrading to CM10. CyanogenMod's support for this phone has been awesome.
Been on the CM10 nightlies ever since they started coming out for the SGS. If you are upgrading from CM9, be warned that you will wind up with a new partition layout and new user data by the time you're done with the upgrade.
Till recently, it was pretty stable and a brilliant release. There was some issue that led to awful battery drain as I kept progressing through the daily builds in the past few weeks. Resolved it by going through a full wipe than just cache wipes.
My phone is 2-years-old now and it has been a good run. For its ruggedness (multiple and frequent drops, couple of dunks in water, clumsy usage), I just don't want to give it up, but it seems like they may have trouble doing CM11 on it.
Do turn off zRAM in the performance options for better stability.
I run CM9 on the same model but I'm reluctant to upgrade on account of the 100+ open issues on the bug tracker[1] and the forum feed-back[2]. I guess I'll wait a little longer.
I have a Samsung Galaxy S (the first one). Since this phone has quite a following I got very lucky: CM has continuously been releasing updates for it, even though it's a very old phone by todays standards. I've been using CM7 on it, now have CM9 installed and am in the progress of upgrading to CM10. CyanogenMod's support for this phone has been awesome.